GeezerVison

Add support for PostgreSQL Row Level Security statements:
- CREATE POLICY with full syntax (FOR, TO, USING, WITH CHECK clauses)
- ALTER TABLE ENABLE/DISABLE/FORCE/NO FORCE ROW LEVEL SECURITY

Changes:
- New CreatePolicy AST class for CREATE POLICY statements
- Added RLS operations to AlterOperation enum
- Updated grammar with POLICY, LEVEL, SECURITY keywords
- Fixed grammar conflicts with LOOKAHEAD directives
- Updated all visitor interfaces and implementations
- Added comprehensive unit tests (19 tests, 100% passing)
- Updated README.md with new features

All code quality checks passing:
- CheckStyle: 0 violations
- PMD: passed

Fixed parser failures when parsing PostgreSQL Row Level Security (RLS)
statements by reordering grammar alternatives to check more specific
patterns before less specific ones.

Problem:
- ALTER TABLE ... ENABLE/DISABLE ROW LEVEL SECURITY failed to parse
- Parser was incorrectly choosing ENABLE/DISABLE KEYS path first
- Grammar warning about WITH keyword conflict in CREATE POLICY

Solution:
1. Reordered ENABLE alternatives: ENABLE ROW LEVEL SECURITY now checked
   before ENABLE KEYS (lines 9674-9684)
2. Reordered DISABLE alternatives: DISABLE ROW LEVEL SECURITY now checked
   before DISABLE KEYS (lines 9661-9671)
3. Added LOOKAHEAD(2) to WITH CHECK clause in CREATE POLICY to resolve
   conflict with CTEs (line 10470)

Impact:
- All 19 existing RLS tests pass (8 AlterRowLevelSecurityTest,
  11 CreatePolicyTest)
- WITH keyword conflict warning eliminated
- Parser can now handle real-world SQL migration files with RLS statements
- No regressions in existing functionality

Technical Note:
In JavaCC, when multiple alternatives share a common prefix (like ENABLE),
the more specific pattern (longer token sequence) must appear FIRST in the
grammar to be matched correctly. LOOKAHEAD values help disambiguate, but
ordering is critical for correct parsing.

Added K_LEVEL, K_POLICY, and K_SECURITY tokens to RelObjectNameWithoutStart()
production to allow these keywords to be used as column aliases in addition to
table/column names. This resolves the conflict where RLS keywords were breaking
Oracle hierarchical queries and keywords-as-identifiers tests.

The fix maintains RLS functionality while allowing these keywords to work in all
SQL contexts including aliases (e.g., SELECT col AS level).

After running `./gradlew updateKeywords`, the task automatically added
LEVEL, POLICY, and SECURITY keywords to RelObjectNameWithoutValue() in
alphabetical order (line 3275).

Removed redundant manual additions from RelObjectName() and
RelObjectNameWithoutStart() that were causing unreachable statement
compilation errors.

The keywords are now properly maintained in the canonical location
(RelObjectNameWithoutValue) and will work as identifiers in all contexts.

Tests: All 4154 tests passing

Add expression visitor calls to traverse USING and WITH CHECK clauses,
enabling discovery of all table references in subqueries.

This completes the TablesNamesFinder visitor implementation for CREATE POLICY
statements by following the same pattern used in Update, Delete, and PlainSelect
statements.

Includes comprehensive test coverage (12 tests) covering simple subqueries,
nested subqueries, CTEs, JOINs, and edge cases.