QueryGroup & DataSourceSrv & DataSourcePicker changes simplify usage, error handling and reduce duplication, support for uid (#29542)

* Starting moving more stuff into data source picker

* WIP progress

* Progress on datasource picker rethink

* Things are working now some details to figure out

* Removed commented part

* Complex work on getting data source lists

* Fixed variable support showing correct data sources

* Tried fixing dashboard import but failed

* Fixes

* Fixed import dashboard

* Fixed unit test

* Fixed explore test

* Fixed test

* Fix

* fixed more tests

* fixed more tests

* fixed showing which option is default in picker

* Changed query variable to use data source picker, updated tests and e2e

* Fixed more tests

* Updated snapshots, had wrong typescript version