Add unserialize() throw type extension - #6528

PhpStorm stubs now declare @throws \TypeError and @throws \ValueError on unserialize(), so every call became an explicit throw point.

On PHP 8.0+, unserialize() throws:

• TypeError / ValueError for invalid $options:
  • allowed_classes that is not array|bool;
  • an allowed_classes entry that is not a valid class name (8.4+);
  • max_depth that is not an int, or is negative.
• TypeError when the data does not fit a typed property (Cannot assign string to property R::$x of type int), whatever the options.

PHP 7 only warns.

The extension decides on native types:

• Without $options, or with a constant options array that is valid: TypeError only.
  • Valid means: allowed_classes is absent, a bool, or a list of constant class-name strings; and max_depth is absent or int<0, max>.
• allowed_classes set to false or []: VoidType. Objects then become __PHP_Incomplete_Class, so no typed property can reject the data (checked on PHP 8.5).
• Anything else, including non-constant options: the declared TypeError|ValueError.

Tests are in CatchWithUnthrownExceptionRuleTest, with separate expectations for PHP 8.0+ and for PHP < 8.0, where every catch is dead. Both fail without the extension; the < 8.0 expectations were verified locally on PHP 7.4.

The PRs for array_chunk(), get_class(), hash(), array_fill() and unserialize() are all based on 2.2.x. They add their test methods at different places in CatchWithUnthrownExceptionRuleTest, so they merge cleanly in any order (checked).

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