Lots of fixes

[tom-wolfe]

Fixed

• The canonical types Postgres renders are no longer refused. tinyint, nchar, nvarchar and binary are written as smallint, character, character varying and bytea, but the engine's vocabulary is read from its own catalog and so never names them, leaving a plan that rendered the column correctly and then refused it as an unresolved type. They now compare equal to the type they are rendered as.
• A varbinary length no longer drifts. bytea carries none, so a declared one was never read back and every plan asked to change the column again.
• A sequence option declared with the default value now settles.
• An identity column reports no minimum where none was declared.
• An identity option reset to the engine's default is now written.
• Changing an identity's increment or minimum no longer restarts its counter. RESTART was appended to every identity alter. Only a start that actually moved carries a RESTART now, and that case is reported as a data hazard.

[github-actions]

✅ NSchema.Postgres

✅ Release

Version 5.6.1 is valid (latest published: 5.6.0).

Changelog entry for 5.6.1 is present.

✅ Tests

All 257 tests passed.