feat: Support Spark expression str_to_map

[unknowntpo]

Which issue does this PR close?

Closes #3168

Rationale for this change

Comet does not yet support Spark StringToMap, so this change wires it through serde and native execution.

What changes are included in this PR?

• wire Spark StringToMap to the native SparkStrToMap UDF
• register SparkStrToMap in the native function registry
• add SQL file coverage for str_to_map

How are these changes tested?

make test-jvm \
  PROFILES="-Drat.skip=true -Dmaven.gitcommitid.skip=true -Dsuites=org.apache.comet.CometSqlFileTestSuite" \
  MAVEN_OPTS="-Dmaven.gitcommitid.skip=true -Drat.skip=true"

[comphead]

to check Comet enabled we need to remove spark_answer_only for all possible queries

[unknowntpo]

fixed.

[comphead]

Thanks @unknowntpo for your contribution, I think to prove it works we need to run test queries with just query to let them run with Comet and also it would be nice to support all datatypes

[unknowntpo]

@comphead Thanks for the review. I updated the SQL tests to use query instead of query spark_answer_only where applicable, so these cases run with Comet as well.

I also added table-column coverage for the string-like input types accepted by str_to_map: STRING, CHAR, and VARCHAR, including cases where the delimiters come from columns.

[comphead]

Thanks @unknowntpo please add the function to docs/source/user-guide/latest/expressions.md

[unknowntpo]

Thanks @unknowntpo please add the function to docs/source/user-guide/latest/expressions.md

Okay, updated.

[comphead]

Thanks @unknowntpo for your contribution, I think it is good to go

[unknowntpo]

Thanks @unknowntpo for your contribution, I think it is good to go

Thanks @comphead for reviewing my code !