feat: aggregate neighbors API #785

Is your feature request related to a problem? Please describe.
I would like to add AggregateNeighbors API that allows to do the following:

• specify the set of vertices
• specify the max traversal depth
• specify the stopping condition
• specify aggregations

On the run it should start traversals from specified vertices until max depth or stopping condition, compute aggregations, return result.

Describe the solution you would like
API in Scala, bindings in PySpark Connect/Classic

Component

• Scala Core Internal
• Scala API
• Spark Connect Plugin
• Infrastructure
• PySpark Classic
• PySpark Connect

Additional context

Are you planning on creating a PR?

• I'm willing to make a pull-request