RBAC: Add required component to perform access control checks for user api when running single tenant (#93104)

* Unexport store and create new constructor function

* Add ResourceAuthorizer and LegacyAccessClient

* Configure checks for user store

* List with checks if AccessClient is configured

* Allow system user service account to read all users

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Co-authored-by: Gabriel MABILLE <gamab@users.noreply.github.com>

pkg/services/accesscontrol/accesscontrol.go

@@ -28,6 +28,10 @@ type AccessControl interface {
 	// RegisterScopeAttributeResolver allows the caller to register a scope resolver for a
 	// specific scope prefix (ex: datasources:name:)
 	RegisterScopeAttributeResolver(prefix string, resolver ScopeAttributeResolver)
+	// WithoutResolvers copies AccessControl without any configured resolvers.
+	// This is useful when we don't want to reuse any pre-configured resolvers
+	// for a authorization call.
+	WithoutResolvers() AccessControl
 }
 
 type Service interface {