[FLINK-38565][table] Reduce TRY_CAST chain if source and target types are same

[snuyanzin]

What is the purpose of the change

The PR allows to reduce useless TRY_CAST e.g.

SELECT TRY_CAST(CAST(a AS STRING) AS STRING) FROM MyTable

will be optimized to

SELECT CAST(a AS STRING) FROM MyTable

also more examples in tests

Brief change log

FlinkConvertletTable and tests

Verifying this change

CalcTest

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:

• 721af2a Azure: SUCCESS

Bot commands

The @flinkbot bot supports the following commands:

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

[dawidwys]

lgtm