PHOENIX-6644 Fix ResultSet.getString(columnName) for view index queries with constant columns

[TheNamesRai]

PHOENIX-6644 Fix ResultSet.getString(columnName) for view index queries with constant columns

Design doc - link

When a view has constant columns in its WHERE clause (e.g., WHERE status='ACTIVE')
and an index is used, ResultSet.getString("status") throws ColumnNotFoundException
while getString(1) works.

Root cause: IndexStatementRewriter converts view constants to literals during
optimization, losing the original column name from RowProjector.reverseIndex.

Solution: Merge column name mappings from the original data plan projector into
the optimized index plan projector in QueryCompiler.

Changes:

• RowProjector: Added constructor accepting additionalNameMappings parameter
  for immutable merging during construction
• RowProjector: Implemented mergeColumnNameMappings() to build and merge
  additional column name mappings without post-construction mutation
• QueryCompiler: Integrate projector merging after ProjectionCompiler in
  compileSingleFlatQuery() when dataPlans contains the optimized TableRef
• ViewIndexColumnNameGetterIT: New comprehensive test suite (6 tests covering
  basic scenario, multiple constants, wildcards, PreparedStatement, subqueries)
• GlobalIndexOptimizationIT: Uncommented previously failing assertion

Testing: 6 new tests + existing suite (39 tests pass: ViewIndexIT, GlobalIndexOptimizationIT)

[TheNamesRai]

All unit tests are passing in my local