[FLINK-39187][table] Add core built-in aggregate functions for BITMAP

[dylanhz]

What is the purpose of the change

This is the fifth PR for FLIP-556, following #27817.

This PR introduces built-in aggregate functions for the BITMAP type, including bitmap-returning aggregations and their cardinality-returning variants.

Brief change log

- [hotfix] Made `RoaringBitmapData` implement `Serializable` and removed unused `wrap` method
- Added `BITMAP_BUILD_AGG` aggregate function with retraction support
- Added `BITMAP_AND_AGG`, `BITMAP_OR_AGG`, `BITMAP_XOR_AGG` aggregate functions with retraction support
- Added cardinality-returning variants (`BITMAP_AND_COUNT`, `BITMAP_OR_COUNT`, `BITMAP_XOR_COUNT`) via abstract base class refactoring
- Added documentation (EN/ZH), Java Table API, and PyFlink bindings for all functions

Verifying this change

This change added tests and can be verified as follows:

- `BitmapAggFunctionITCase`: Integration tests for all 7 aggregate functions covering null handling, retraction, boundary values, oversize bitmap, and validation errors
- Scala ITCase tests covering batch/streaming group-by, over-window, tumble window, and Table API aggregation scenarios

Does this pull request potentially affect one of the following parts:

• Dependencies (does it add or upgrade a dependency): no
• The public API, i.e., is any changed class annotated with @Public(Evolving): yes
• The serializers: no
• The runtime per-record code paths (performance sensitive): no
• Anything that affects deployment or recovery: JobManager (and its components), Checkpointing, Kubernetes/Yarn, ZooKeeper: no
• The S3 file system connector: no

Documentation

• Does this pull request introduce a new feature? yes
• If yes, how is the feature documented? JavaDocs

[flinkbot]

CI report:

• 0a95c88 Azure: SUCCESS

Bot commands

The @flinkbot bot supports the following commands:

• @flinkbot run azure re-run the last Azure build