SQL DDL transformations and more

Changes for 1.64 - 2023-12-22

• support EXCLUDE constraints in Postgres (thansk @KES777)
• Improve enums in the PostgrSQL family (thanks @nrdvana)
• Add index length options for MySQL (thanks @abeverley)
• FIXES
• fix spurious on_update/on_delete in diffs (thanks @nrdvana)
• CI improvements (thanks @eserte)
• AUTOINCREMENT is now correctly parsed for SQLite (thanks @nrdvana)