Use type/JSON for field base_type for postgres and mysql (#28849)

* Use type/JSON instead of type/SerializedJSON

* Tidy migration

* Update migration

* Fix rollback migration for h2

* whitespace

* Add test for migration

* Fix test

* Add rollback

* whitespace

* Test JSONB type as well as JSON

* Don't fingerprint JSON columns

* Remove comment, that might be wrong in the future

* Update test

* Add tests for fingerprinting

* Use base-type JSON for fingerprinting base query

* Add test for visibility-type=details-only

* undo .

* Change migration id

* Fix migration test

* Merge master

* Exclude mariadb from tests

* Make is-mariadb? public