Add GET /api/database/{id}/syncable_schemas endpoint (#30529)

* Add `include_empty` parameter to GET /api/database/{id}/schemas endpoint

* Reuse filtered-syncable-schemas

* Add schemas driver feature flag

* Add comment

* Add driver specific tests for all-schemas

* Fix kondo

* Revert "Add schemas driver feature flag"

This reverts commit 91474aff84dfb7e47f392de5836c0d18a508b23f.

* Rename to syncable-schemas and create new endpoint

* syncable-schemas default impl

* Update tests

* Add multimethod to driver changelog

* Fix Tamas' suggestions