[FLINK-39186][table] Add core built-in scalar functions for BITMAP

[dylanhz]

What is the purpose of the change

This is the fourth PR for FLIP-556, following #27778.

This PR introduces built-in scalar functions for the BITMAP type, BITMAP literal support in Table API, and comprehensive BITMAP cast tests.

Brief change log

• Added 10 built-in scalar functions: BITMAP_BUILD, BITMAP_FROM_BYTES, BITMAP_TO_BYTES, BITMAP_TO_ARRAY, BITMAP_TO_STRING, BITMAP_CARDINALITY, BITMAP_AND, BITMAP_ANDNOT, BITMAP_OR, BITMAP_XOR
• Supported BITMAP literal in Table API via BITMAP_FROM_BYTES(serialized_bytes) in ApiExpressionUtils
• Added BITMAP cast it cases in CastFunctionITCase and CastFunctionMiscITCase
• 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:

• BitmapFunctionsITCase: Integration tests for all 10 functions covering null handling, boundary values, runtime errors, and validation errors
• CastFunctionITCase / CastFunctionMiscITCase: BITMAP cast it cases covering all logical types and truncation/padding behavior

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 (BaseExpressions)
• 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? docs / JavaDocs

[flinkbot]

CI report:

• 34083d6 Azure: SUCCESS
• 24fd357 Azure: PENDING

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