IAM: Create and delete user from the legacy store (#107694)

* Add Create for User + DualWriter setup

* Add delete User

* Fix delete + access check

* Add tests for delete user

* Add tests for create user

* Fixes

* Use sqlx session to fix database locked issues

* wip authz checks

* legacyAccessClient

* Update legacyAccessClient, add tests for create user

* Close rows before running other queries

* Use ExecWithReturningId

* Verify deletion in the tests

* Add Validate and Mutate

* Other changes

* Address feedback

* Update tests

---------

Co-authored-by: Gabriel Mabille <gabriel.mabille@grafana.com>

pkg/tests/apis/iam/testdata/user-test-create-v0.yaml

@@ -0,0 +1,10 @@
+apiVersion: iam.grafana.app/v0alpha1
+kind: User
+metadata:
+  namespace: default
+  name: abcdefghijkl
+spec:
+  email: testuser1@example123.com
+  login: testuser1
+  name: Test User 1
+  provisioned: false