[KYUUBI #5505][FLINK] Support HELP command

[YesOrNo828]

Why are the changes needed?

resolve: #5505

Show available commands when users type 'HELP;' in the beeline.

Solution:

• Using ExtendedParser parse statement and return Operation of Flink engine.
• Check whether the operation is HelpOperation or not.
• dependency on flink-table-planner-loader.jar.

Why not using Flink SQL Client Parser(SqlCommandParserImpl) to obtain the Command enum?

Flink 1.16's approach:

val opt:Optional[Operation] = org.apache.flink.table.client.cli.SqlCommandParserImpl.parseCommand()
check opt.get() instance of HelpOperation or not
if yes return CliStrings.MESSAGE_HELP

Flink 1.17 & 1.18

val opt: Optional[Command] = org.apache.flink.table.client.cli.parser.SqlCommandParserImpl.parseStatement()
check opt.get() is Command.HELP or not
if yes return CliStrings.MESSAGE_HELP

The Command class is added from Flink1.17;
The SqlCommandParserImpl package is changed, and the method name is changed from Flink1.17;

This approach requires distinguishing between different Flink versions and maintaining both implementations.
It's more complicated, so abandoned.

How was this patch tested?

• Add some test cases that check the changes thoroughly including negative and positive cases if possible

• Add screenshots for manual tests if appropriate

• Run test locally before make a pull request

Was this patch authored or co-authored using generative AI tooling?

[codecov-commenter]

Codecov Report

Merging #5585 (e73b15e) into master (591250c) will decrease coverage by 0.29%.
Report is 26 commits behind head on master.
The diff coverage is n/a.

@@             Coverage Diff              @@
##             master    #5585      +/-   ##
============================================
- Coverage     61.69%   61.40%   -0.29%     
  Complexity       23       23              
============================================
  Files           603      603              
  Lines         35670    35635      -35     
  Branches       4869     4874       +5     
============================================
- Hits          22005    21883     -122     
- Misses        11281    11370      +89     
+ Partials       2384     2382       -2     

see 43 files with indirect coverage changes

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[pan3793]

LGTM, except to one minor comment

[link3280]

Thanks for the PR! I left some comments please kindly take a look. @YesOrNo828

[link3280]

@YesOrNo828 Merged. Thanks!