Support SQL Server table variables through shared table references

[minleejae]

SELECT columnName FROM @table and DML targeting a declared table variable fail to parse. Add a shared table-reference production for query sources and DML targets, and reuse the existing alias production for UPDATE's table/index-hint path.

Table references carry an explicit tableVariable flag while preserving existing Table-based APIs and visitor/deparser dispatch. Cloning preserves the flag, default catalog/schema qualification leaves local references alone, and TablesNamesFinder separates local variables from catalog tables while retaining them in findTablesOrOtherSources. Validation checks the SQL Server table-variable feature and skips catalog-table metadata lookups for these references.

Catalog-only grammar remains unchanged. This adds parsing and reference classification; declaration binding and table-variable column/type resolution are outside this change.

Validation: full Gradle check and Maven verify; SELECT/JOIN/CTE, INSERT, UPDATE, DELETE and MERGE roundtrips, existing DML models, metadata lookups, dialect validation, cloning/qualification, scalar variables, declarations and following statements, normal tables/index hints, and unsupported catalog-only forms.

Syntax reference: Microsoft table documentation.

Fixes #911.

[manticore-projects]

Thank you!