[CI] Optimize `admin > databases` E2E tests (#29418) (#29831)

* Rework repro for 16382

* Merge multiple "connection settings" tests together

* Merge multiple "scheduling settings" tests together

* Merge tiny test with the main body

* Remove redundant tests

* Rework the sample database action sidebar

* Handle database exceptions in one spec

* Move stray database test to exceptions spec

* Move Postgres SSL test to external

* Group together Google service account JSON tests

* Custom caching

* Move remaining pieces of add to external

* Rename spec to `add-new-database`

* Move repro for 20471 to exceptions

* Add segments and metrics to the database we want to delete

* Add `visitDatabase` helper

Co-authored-by: Nemanja Glumac <31325167+nemanjaglumac@users.noreply.github.com>