Replace signed in user for identity.requester (#73750)

* Make identity.Requester available at Context

* Clean pkg/services/guardian/guardian.go

* Clean guardian provider and guardian AC

* Clean pkg/api/team.go

* Clean ctxhandler, datasources, plugin and live

* Question: what to do with the UserDisplayDTO?

* Clean dashboards and guardian

* Remove identity.Requester from ReqContext

* Implement NewUserDisplayDTOFromRequester

* Fix tests

* Change status code numbers for http constants

* Upgrade signature of ngalert services

* log parsing errors instead of throwing error

* Fix tests and add logs

* linting

pkg/expr/transform.go

@@ -8,8 +8,8 @@ import (
 
 	"github.com/grafana/grafana-plugin-sdk-go/backend"
 
+	"github.com/grafana/grafana/pkg/services/auth/identity"
 	"github.com/grafana/grafana/pkg/services/datasources"
-	"github.com/grafana/grafana/pkg/services/user"
 )
 
 // Request is similar to plugins.DataQuery but with the Time Ranges is per Query.
@@ -18,7 +18,7 @@ type Request struct {
 	Debug   bool
 	OrgId   int64
 	Queries []Query
-	User    *user.SignedInUser
+	User    identity.Requester
 }
 
 // Query is like plugins.DataSubQuery, but with a a time range, and only the UID