Add function name as identifier in antlr

[penghuo]

Signed-off-by: Peng Huo penghuo@gmail.com

Description

• Add function name as identifier in ANTLR.
• Remove literal function support, includes
  • current_timestamp
  • localtimestamp
  • localtime
  • current_time
  • current_date

Issues Resolved

opensearch-project/observability#828
#672

Check List

• New functionality includes testing.
  • All tests pass, including unit test, integration test and doctest
• New functionality has been documented.
  • New functionality has javadoc added
  • New functionality has user manual doc added
• Commits are signed per the DCO using --signoff

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.
For more information on following Developer Certificate of Origin and signing off your commits, please check here.

[codecov-commenter]

Codecov Report

Merging #1015 (9cf1e90) into 2.x (21373b9) will decrease coverage by 2.63%.
The diff coverage is 100.00%.

@@             Coverage Diff              @@
##                2.x    #1015      +/-   ##
============================================
- Coverage     98.22%   95.58%   -2.64%     
+ Complexity     3272     3268       -4     
============================================
  Files           314      324      +10     
  Lines          8205     8855     +650     
  Branches        535      652     +117     
============================================
+ Hits           8059     8464     +405     
- Misses          142      334     +192     
- Partials          4       57      +53     

Flag	Coverage Δ
query-workbench	62.76% <ø> (?)
sql-engine	98.21% <100.00%> (-0.01%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
...pensearch/sql/ppl/parser/AstExpressionBuilder.java	100.00% <100.00%> (ø)
...pensearch/sql/sql/parser/AstExpressionBuilder.java	100.00% <100.00%> (ø)
workbench/public/application.tsx	0.00% <0.00%> (ø)
workbench/public/components/Main/main.tsx	53.00% <0.00%> (ø)
...h/public/components/QueryLanguageSwitch/Switch.tsx	85.71% <0.00%> (ø)
workbench/public/utils/PanelWrapper.tsx	100.00% <0.00%> (ø)
workbench/public/components/SQLPage/SQLPage.tsx	100.00% <0.00%> (ø)
...ublic/components/QueryResults/QueryResultsBody.tsx	68.32% <0.00%> (ø)
workbench/public/components/app.tsx	0.00% <0.00%> (ø)
...ch/public/components/QueryResults/QueryResults.tsx	61.60% <0.00%> (ø)
... and 2 more

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[dai-chen]

Thanks for the changes!