[FLINK-29081][table-planner] capitalize join hints

[xuyangzhong]

What is the purpose of the change

Currently, join hint will not be identified with low case. This pr tries to fix this.

Brief change log

• Capitalize join hints when convert SqlNode to RelNode

Verifying this change

Some tests are added to verify this pr.

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?

[flinkbot]

CI report:

• cceeffa Azure: SUCCESS

Bot commands

The @flinkbot bot supports the following commands:

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

[godfreyhe]

LGTM, please fix the failed tests

[xuyangzhong]

@flinkbot run azure

[xuyangzhong]

@flinkbot run azure