Fix action database picker state without available databases (#29039)

* Fix empty database picker state

* Remove redundant `requireWriteback` occurrences

* Update test

* Update test

* Use clearer names

* Don't show query language message for actions

* Use database `hasActionsEnabled` method

* Remove `requireWriteback` prop

* Respect `readOnly` prop in `DataSourceSelectors`

* Extend e2e test coverage

* Use `setActionsEnabledForDB` in Cypress

* Fix data picker behavior