[FLINK-39402][table] Fix LIKE quick path ignoring default escape character '\'

[Au-Miner]

What is the purpose of the change

Fix the default escape character \ not being applied in LIKE's quick path when no ESCAPE clause is specified, causing 'TE%ST' LIKE 'TE\%ST' to incorrectly return FALSE while 'TE_ST' LIKE 'TE\_ST' correctly returns TRUE.

Brief change log

• Unified escape character handling in LikeCallGen for both 2-operand and 3-operand cases using Option[Char]
• Added test cases for default escape \ and empty ESCAPE scenarios in ScalarFunctionsTest

Verifying this change

This change is verified by new and existing tests in ScalarFunctionsTest#testLike and ScalarFunctionsTest#testLikeWithEscape.

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): no
• 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? no
• If yes, how is the feature documented? not applicable

[flinkbot]

CI report:

• 39d7d5b Azure: FAILURE

Bot commands

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[raminqaf]

Thanks for the contribution @Au-Miner! I left a comment for a test case!

[raminqaf]

Can we add a test for this case please

'abc_def' LIKE 'abc_def' ESCAPE ''