Support PostgreSQL text search configuration DDL

[minleejae]

PostgreSQL text-search configuration DDL was unsupported, so schema scripts containing COPY/PARSER definitions or mapping changes could not be parsed.

Add structured CREATE/ALTER TEXT SEARCH CONFIGURATION nodes for COPY/PARSER sources, ADD/ALTER/DROP MAPPING, scoped or global dictionary replacement, and rename/owner/schema changes. Reuse qualified-name and identifier-list parsing, and wire statement visitors, deparsing and feature validation. Configuration/parser/dictionary names are kept separate from table references.

Tests cover the mapping forms, quoted COPY sources, dictionary lists, AST mutation, invalid input, and statement boundaries. Twelve additional scenarios were executed on PostgreSQL 18.6; configuration metadata and ordered token-to-dictionary mappings match for original SQL and both rendered forms.

Syntax references: CREATE TEXT SEARCH CONFIGURATION, ALTER TEXT SEARCH CONFIGURATION.

Validation: focused tests, JavaCC ambiguity checks, Checkstyle and Spotless on this independent branch. The combined implementation also passes the full Gradle check and Maven verify; the 1,304-input prior regression corpus has no previously successful input regressions.