Avatical Removal Part1: remove Avatica dependency from metadata conversion flow

[carsheng]

This change accomplishes Part 1 of removing Avatica from the datacloud-jdbc driver - specifically focusing on marshalling of column metadata. It removes Avatica dependencies from metadata conversion and introduces a custom SimpleResultSet implementation for database metadata queries which includes much of the JDBc boilerplate that was originally handled by Avatica.
QueryMetadataUtil now uses SimpleMetadataResultSet.of() instead of Avatica-based constructors, and type mappings were updated to use standard JDBCType instead of Avatica's SqlType enum.

[codecov]

Codecov Report

❌ Patch coverage is 83.65180% with 77 lines in your changes missing coverage. Please review.
✅ Project coverage is 82.34%. Comparing base (f8d84ab) to head (6bae705).
⚠️ Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
...datacloud/jdbc/core/resultset/SimpleResultSet.java	73.07%	13 Missing and 15 partials ⚠️
...core/resultset/ResultSetWithPositionalGetters.java	35.29%	22 Missing ⚠️
...e/datacloud/jdbc/core/SimpleMetadataResultSet.java	76.78%	7 Missing and 6 partials ⚠️
...ud/jdbc/core/metadata/SimpleResultSetMetaData.java	85.36%	3 Missing and 3 partials ⚠️
...alesforce/datacloud/jdbc/core/MetadataSchemas.java	95.45%	2 Missing ⚠️
...esforce/datacloud/jdbc/core/QueryMetadataUtil.java	92.30%	2 Missing ⚠️
...force/datacloud/jdbc/core/metadata/ColumnType.java	92.30%	1 Missing and 1 partial ⚠️
...loud/jdbc/core/resultset/ForwardOnlyResultSet.java	87.50%	1 Missing and 1 partial ⚠️

❌ Your patch status has failed because the patch coverage (83.65%) is below the target coverage (90.00%). You can increase the patch coverage or adjust the target coverage.

Additional details and impacted files

@@             Coverage Diff              @@
##               main     #136      +/-   ##
============================================
- Coverage     82.79%   82.34%   -0.46%     
- Complexity     1347     1549     +202     
============================================
  Files           111      117       +6     
  Lines          4058     4328     +270     
  Branches        413      442      +29     
============================================
+ Hits           3360     3564     +204     
- Misses          508      549      +41     
- Partials        190      215      +25     

Components	Coverage Δ
JDBC Core	83.32% <83.65%> (-0.67%)	⬇️
JDBC Main	40.69% <ø> (ø)
JDBC HTTP	91.09% <ø> (ø)
JDBC Utilities	66.07% <ø> (ø)
Spark Datasource	∅ <ø> (∅)

Files with missing lines	Coverage Δ
.../datacloud/jdbc/core/resultset/ColumnAccessor.java	100.00% <100.00%> (ø)
...tacloud/jdbc/core/resultset/ReadOnlyResultSet.java	100.00% <100.00%> (ø)
...e/datacloud/jdbc/util/ArrowToColumnTypeMapper.java	62.26% <100.00%> (ø)
...com/salesforce/datacloud/jdbc/util/ArrowUtils.java	84.44% <ø> (+0.31%)	⬆️
...alesforce/datacloud/jdbc/core/MetadataSchemas.java	95.45% <95.45%> (ø)
...esforce/datacloud/jdbc/core/QueryMetadataUtil.java	91.45% <92.30%> (-0.18%)	⬇️
...force/datacloud/jdbc/core/metadata/ColumnType.java	88.75% <92.30%> (ø)
...loud/jdbc/core/resultset/ForwardOnlyResultSet.java	87.50% <87.50%> (ø)
...ud/jdbc/core/metadata/SimpleResultSetMetaData.java	85.36% <85.36%> (ø)
...e/datacloud/jdbc/core/SimpleMetadataResultSet.java	76.78% <76.78%> (ø)
... and 2 more

... and 1 file with indirect coverage changes

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[KaviarasuSakthivadivel]

I believe these will improve coverage:

1. Add tests for ResultSetWithPositionalGetters string-based accessors
2. Test all type conversion edge cases in SimpleResultSet
3. Add negative test cases (closed ResultSet, invalid columns, null data)