feat: add lower() and lcase()

[Liu-2001]

• What kind of change does this PR introduce? (Bug fix, feature, docs update, ...)

  Adds the lcase() and lower() functions.

• What is the current behavior? (You can also link to an open issue here)

  The two functions have not been implemented.

  close built-in function: Supportlcase() and lower() #784

• What is the new behavior (if this is a feature change)?
  These two functions convert all characters in a string into lower cases.

[github-actions]

Linux Test Report

  49 files    49 suites   4m 22s ⏱️
122 tests 119 ✔️ 3 💤 0 ❌
151 runs  148 ✔️ 3 💤 0 ❌

Results for commit 56f5827.

♻️ This comment has been updated with latest results.

[github-actions]

HybridSE Linux Test Report

       65 files       231 suites   6m 34s ⏱️
19 107 tests 19 107 ✔️ 0 💤 0 ❌

Results for commit 56f5827.

♻️ This comment has been updated with latest results.

[github-actions]

HybridSE Mac Test Report

       65 files       231 suites   6m 32s ⏱️
19 107 tests 19 107 ✔️ 0 💤 0 ❌

Results for commit 56f5827.

♻️ This comment has been updated with latest results.

[codecov]

Codecov Report

Merging #1192 (543c497) into main (963f29b) will increase coverage by 0.00%.
The diff coverage is 100.00%.

❗ Current head 543c497 differs from pull request most recent head 56f5827. Consider uploading reports for the commit 56f5827 to get more accurate results

@@            Coverage Diff            @@
##               main    #1192   +/-   ##
=========================================
  Coverage     42.91%   42.92%           
  Complexity      279      279           
=========================================
  Files           562      562           
  Lines        106006   106074   +68     
  Branches        983      985    +2     
=========================================
+ Hits          45492    45527   +35     
- Misses        60333    60364   +31     
- Partials        181      183    +2     

Impacted Files	Coverage Δ
hybridse/src/udf/udf.h	100.00% <ø> (ø)
hybridse/src/codegen/udf_ir_builder_test.cc	99.43% <100.00%> (+<0.01%)	⬆️
hybridse/src/udf/default_udf_library.cc	96.24% <100.00%> (+0.02%)	⬆️
hybridse/src/udf/udf.cc	84.95% <100.00%> (+0.19%)	⬆️
...m/openmldb/taskmanager/spark/SparkJobManager.scala	50.90% <0.00%> (-2.04%)	⬇️
src/cmd/sql_cmd.h	0.00% <0.00%> (ø)
src/sdk/sql_cluster_router.cc	0.00% <0.00%> (ø)
...4paradigm/openmldb/batch/api/OpenmldbSession.scala	0.00% <0.00%> (ø)
hybridse/src/planv2/ast_node_converter.cc	94.12% <0.00%> (+<0.01%)	⬆️
hybridse/src/testing/engine_test_base.cc	80.54% <0.00%> (+0.04%)	⬆️
... and 3 more

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 963f29b...56f5827. Read the comment docs.

[jingchen2222]

Great Job! @Liu-2001 Thank you for the contribution.
@wuyou10206 Add tests for lower() and lcase() function once the PR has been merged

LGTM