fix(parser): model PostgreSQL declarative partitions

[minleejae]

Summary

• add a shared structured partition-bound model for RANGE, LIST, HASH, and DEFAULT partitions
• support ordered multi-column PARTITION BY keys and CREATE TABLE ... PARTITION OF
• model ALTER TABLE ... ATTACH PARTITION and DETACH PARTITION, including CONCURRENTLY and FINALIZE
• update both statement rendering and deparser paths

The CREATE and ALTER changes are combined because they depend on the same partition-bound AST.

Testing

• ./gradlew check

Fixes #2522
Fixes #2523

AI assistance

OpenAI Codex assisted with the implementation and test coverage. The changes were manually reviewed and verified against PostgreSQL syntax.

[manticore-projects]

Thank you!