Provisioning: Allows specifying uid for datasource and use that in derived fields (#23585)

* Add uid to datasource

* Fix uid passing when provisioning

* Better error handling and Uid column type change

* Fix test and strict null error counts

* Add backend tests

* Add tests

* Fix strict null checks

* Update test

* Improve tests

* Update pkg/services/sqlstore/datasource.go

Co-Authored-By: Arve Knudsen <arve.knudsen@gmail.com>

* Variable rename

Co-authored-by: Arve Knudsen <arve.knudsen@gmail.com>

pkg/services/provisioning/datasources/testdata/all-properties/all-properties.yaml

@@ -24,6 +24,7 @@ datasources:
       tlsClientKey: "ZkN4aG1aNkja/gKAB1wlnKFIsy2SRDq4slrM0A=="
     editable: true
     version: 10
+    uid: "test_uid"
 
 deleteDatasources:
   - name: old-graphite3