fix(sdk/metric): Fix data race with initialization of NewPeriodicReader - #9028

This release contains the first stable release of the OpenTelemetry Go
Logs API and SDK.
Our project stability guarantees now apply to the following modules:

- `go.opentelemetry.io/otel/log`
- `go.opentelemetry.io/otel/sdk/log`

See our [versioning
policy](https://github.com/open-telemetry/opentelemetry-go/blob/main/VERSIONING.md)
for more information about these stability guarantees.

### Added

- Add `String` method for `KeyValue` type in
`go.opentelemetry.io/otel/attribute`. (#8205)
- Add `String` method for `Set` type in
`go.opentelemetry.io/otel/attribute`. (#8347)
- Add `WithMaxExportBatchSize` to `go.opentelemetry.io/otel/sdk/metric`
to configure the maximum export batch size for `PeriodicReader`. (#8960)
- Add `WithAttributeValueDepthLimit`, `DefaultAttributeValueDepthLimit`,
and `SpanLimits.AttributeValueDepthLimit` in
`go.opentelemetry.io/otel/sdk/trace` to configure the maximum depth of
span, event, link, and instrumentation scope attribute values. (#8938)
- Add `WithAttributeValueDepthLimit` in
`go.opentelemetry.io/otel/sdk/log` to configure the maximum depth of log
record and instrumentation scope attribute values. (#8938)
- Add `WithMaxResponseSize` to
`go.opentelemetry.io/otel/exporters/otlp/otlptrace/otlptracehttp`,
`go.opentelemetry.io/otel/exporters/otlp/otlpmetric/otlpmetrichttp`, and
  `go.opentelemetry.io/otel/exporters/otlp/otlplog/otlploghttp`. (#8941)
- Add experimental `ProbabilitySampler` in
`go.opentelemetry.io/otel/sdk/trace/x` that conforms to the
[OpenTelemetry specification's threshold-based sampling
algorithm](https://opentelemetry.io/docs/specs/otel/trace/sdk/#probabilitysampler).
(#8123)
- Add experimental `*Binder` extension interfaces in
`go.opentelemetry.io/otel/metric/x` for instruments that support binding
attributes ahead of time. (#8760)
- Add the experimental `Finisher` synchronous metric instrument
extension interface to `go.opentelemetry.io/otel/metric/x`. (#8906)

### Changed

- Use the [OpenTelemetry Attribute Collection representation for
non-OTLP
protocols](https://opentelemetry.io/docs/specs/otel/common/#attribute-collection-representation-for-non-otlp)
for metric data diffs in
`go.opentelemetry.io/otel/sdk/metric/metricdata/metricdatatest`. (#8993)
- Apply a maximum depth of 64 by default to span, event, link, log
record, and instrumentation scope attribute values in
`go.opentelemetry.io/otel/sdk/trace` and
`go.opentelemetry.io/otel/sdk/log`. (#8938)
- Reduce allocations when applying attribute value length limits in
`go.opentelemetry.io/otel/sdk/trace` and
`go.opentelemetry.io/otel/sdk/log` by rebuilding composite values only
when truncation is needed. (#8912)
- Decode `traceparent` using a hex lookup table in
`go.opentelemetry.io/otel/propagation`, which rejects the
specification-disallowed upper-case characters without a separate scan
of the header. (#8739)
- Decode all characters at constant indices in `TraceIDFromHex` and
`SpanIDFromHex` in `go.opentelemetry.io/otel/trace` to eliminate bounds
checks. (#8740)

### Fixed

- Count valid U+FFFD replacement characters toward attribute value
length limits in `go.opentelemetry.io/otel/trace`,
`go.opentelemetry.io/otel/sdk/trace`, and
`go.opentelemetry.io/otel/sdk/log`.
- Truncate string attribute values to empty strings when the configured
length limit is zero, including malformed UTF-8, in
`go.opentelemetry.io/otel/trace`, `go.opentelemetry.io/otel/sdk/trace`,
and `go.opentelemetry.io/otel/sdk/log`. (#9054)
- Fix a data race in `NewPeriodicReader` where `r.inst` was assigned
after the background goroutine was launched in
`go.opentelemetry.io/otel/sdk/metric`. (#9028)
- Prevent precision loss for large `int64` values in `Sum`, `Histogram`,
and `ExponentialHistogram` aggregations in
`go.opentelemetry.io/otel/sdk/metric`. (#8981)
- Ensure `grpc.DialOption` values passed via `WithDialOption` take
precedence over conflicting internally-computed defaults in
  `go.opentelemetry.io/otel/exporters/otlp/otlplog/otlploggrpc`,
`go.opentelemetry.io/otel/exporters/otlp/otlpmetric/otlpmetricgrpc`, and
`go.opentelemetry.io/otel/exporters/otlp/otlptrace/otlptracegrpc`.
(#8805, #8834, #8836)
- Treat overflowing `OTEL_METRIC_EXPORT_INTERVAL` and
`OTEL_METRIC_EXPORT_TIMEOUT` values as invalid in
`go.opentelemetry.io/otel/sdk/metric`. (#8800)
- Prevent a panic in `NewFixedSizeReservoir` and
`FixedSizeReservoirProvider` when given a negative size in
`go.opentelemetry.io/otel/sdk/metric/exemplar`; negative sizes are now
clamped to zero, consistent with a size of zero. (#8832)
- Preserve exponential histogram `ZeroThreshold` during OTLP metric
export in `go.opentelemetry.io/otel/exporters/otlp/otlpmetric`. (#8801)
- Ensure metric helpers in `go.opentelemetry.io/otel/semconv/v1.32.0`,
`go.opentelemetry.io/otel/semconv/v1.33.0`, and
`go.opentelemetry.io/otel/semconv/v1.34.0` record measurements only once
when no attributes are provided. (#8849)
- Treat empty `OTEL_TRACES_SAMPLER` and `OTEL_TRACES_SAMPLER_ARG` values
as unset in `go.opentelemetry.io/otel/sdk/trace`. (#8873)
- Normalize global `OTEL_EXPORTER_OTLP_ENDPOINT` path joining in
`go.opentelemetry.io/otel/exporters/otlp/otlplog/otlploghttp` so
trailing-slash base URLs do not produce double-slash log export paths.
(#8864)
- Prevent a deadlock when formatting an error passed to `RecordError`
calls back into the span in `go.opentelemetry.io/otel/sdk/trace`.
(#8815)
- Prevent `SimpleSpanProcessor.Shutdown` from panicking when constructed
with a nil exporter in `go.opentelemetry.io/otel/sdk/trace`. (#8844)
- Propagate invalid exponential histogram scale errors to Prometheus
exporter self-observability metrics in
`go.opentelemetry.io/otel/exporters/prometheus`. (#8839)
- Retain instrument advisory attributes configured with
`go.opentelemetry.io/otel/metric/x.WithDefaultAttributes` when a
matching View in `go.opentelemetry.io/otel/sdk/metric` does not specify
an attribute filter. (#8859)
- Ignore HTTP URL paths when building OTLP/gRPC metric exporter targets
from `OTEL_EXPORTER_OTLP_ENDPOINT` and
`OTEL_EXPORTER_OTLP_METRICS_ENDPOINT`, while preserving `unix://` and
`unix-abstract://` targets; treat `unix-abstract://` endpoints as
insecure in
`go.opentelemetry.io/otel/exporters/otlp/otlpmetric/otlpmetricgrpc` and
`go.opentelemetry.io/otel/exporters/otlp/otlpmetric/otlpmetrichttp`.
(#8862)
- Ignore HTTP(S) paths when deriving gRPC trace exporter endpoints from
`OTEL_EXPORTER_OTLP_ENDPOINT` and `OTEL_EXPORTER_OTLP_TRACES_ENDPOINT`
in `go.opentelemetry.io/otel/exporters/otlp/otlptrace/otlptracegrpc`.
(#8852)
- Bound memory used while parsing dense W3C property metadata by storing
it compactly and materializing `Property` values on demand in
`go.opentelemetry.io/otel/baggage` and
`go.opentelemetry.io/otel/propagation`.

### Removed

- Remove the experimental `OTEL_GO_X_METRIC_EXPORT_BATCH_SIZE`
environment variable in `go.opentelemetry.io/otel/sdk/metric`.
  Use the `WithMaxExportBatchSize` option instead. (#8960)