Auth: Use sessionStorage instead of cookie for automatic redirection (#92759)

* WIP: working as expected, has to be tested

* Rename query param, small changes

* Remove unused code

* Address feedback

* Cleanup

* Use the feature toggle to control the behaviour

* Use the toggle on the FE too

* Prevent the extra redirect/reload

 Co-authored-by: Josh Hunt <joshhunt@users.noreply.github.com>

* Return to login if user is not authenticated

* Add tracking issue

* Align BE redirect constructor to locationSvc

pkg/api/common_test.go

@@ -191,6 +191,7 @@ func getContextHandler(t *testing.T, cfg *setting.Cfg) *contexthandler.ContextHa
 		cfg,
 		tracing.InitializeTracerForTest(),
 		&authntest.FakeService{ExpectedIdentity: &authn.Identity{ID: "0", Type: claims.TypeAnonymous, SessionToken: &usertoken.UserToken{}}},
+		featuremgmt.WithFeatures(),
 	)
 }