[FLINK-29750][connector-jdbc] Improve PostgresCatalog#listTables() by reusing resources

[liuml07]

What is the purpose of the change

Currently the PostgresCatalog#listTables() creates a new connection and prepared statement for every schema and table when listing tables. This can be optimized by reusing those resources.

Brief change log

(for example:)

• Introduce extractColumnValuesByStatement in base class AbstractJdbcCatalog
• Reuse connection and prepared in PostgresCatalog#listTables()

Verifying this change

Please make sure both new and modified tests in this PR follows the conventions defined in our code quality guide: https://flink.apache.org/contributing/code-style-and-quality-common.html#testing

(Please pick either of the following options)

This change is already covered by existing tests, such as PostgresCatalogTest.

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

• Dependencies (does it add or upgrade a dependency): (yes / no)
• The public API, i.e., is any changed class annotated with @Public(Evolving): (yes / no)
• The serializers: (yes / no / don't know)
• The runtime per-record code paths (performance sensitive): (yes / no / don't know)
• Anything that affects deployment or recovery: JobManager (and its components), Checkpointing, Kubernetes/Yarn, ZooKeeper: (yes / no / don't know)
• The S3 file system connector: (yes / no / don't know)

Documentation

• Does this pull request introduce a new feature? (yes / no)
• If yes, how is the feature documented? (not applicable / docs / JavaDocs / not documented)

[liuml07]

CC @RocMarshal @twalthr

[flinkbot]

CI report:

• 57b8bd4 Azure: SUCCESS

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[MartijnVisser]

We've now moved the code from the JDBC connector to its own dedicated repository; please re-route this PR to https://github.com/apache/flink-connector-jdbc

[liuml07]

Sounds good. Should we remove the connector code from this Flink repo?

[MartijnVisser]

Sounds good. Should we remove the connector code from this Flink repo?

Not yet, that's planned after a release of the JDBC connector and a discussion on the mailing list. But that hopefully should happen quickly.

[liuml07]

Moved to apache/flink-connector-jdbc#4