Alerting: Add recording rule target datasource support to Prometheus conversion API (#101799)

What is this feature?

Adds target datasource UID to the recording rules so that they write to the same datasource used for alerting rule queries after the import.

Why do we need this feature?

Target datasourse support was added in #101678, and under a feature flag grafanaManagedRecordingRulesDatasources (#101778).

This PR makes the importing process:
    Check if the import contains recording rules
    Verify both recording rules and the grafanaManagedRecordingRulesDatasources feature flag are enabled
    If either check fails, return an error
    If both checks pass, create recording rules with the provided datasource UID set as both the query and target datasource

pkg/tests/api/alerting/api_convert_prometheus_test.go

@@ -108,7 +108,8 @@ func TestIntegrationConvertPrometheusEndpoints(t *testing.T) {
 			EnableUnifiedAlerting: true,
 			DisableAnonymous:      true,
 			AppModeProduction:     true,
-			EnableFeatureToggles:  []string{"alertingConversionAPI"},
+			EnableFeatureToggles:  []string{"alertingConversionAPI", "grafanaManagedRecordingRulesDatasources", "grafanaManagedRecordingRules"},
+			EnableRecordingRules:  true,
 		})
 
 		grafanaListedAddr, env := testinfra.StartGrafanaEnv(t, dir, gpath)
@@ -219,7 +220,8 @@ func TestIntegrationConvertPrometheusEndpoints_UpdateRule(t *testing.T) {
 			EnableUnifiedAlerting: true,
 			DisableAnonymous:      true,
 			AppModeProduction:     true,
-			EnableFeatureToggles:  []string{"alertingConversionAPI"},
+			EnableFeatureToggles:  []string{"alertingConversionAPI", "grafanaManagedRecordingRulesDatasources", "grafanaManagedRecordingRules"},
+			EnableRecordingRules:  true,
 		})
 
 		grafanaListedAddr, env := testinfra.StartGrafanaEnv(t, dir, gpath)
@@ -305,7 +307,8 @@ func TestIntegrationConvertPrometheusEndpoints_Conflict(t *testing.T) {
 			EnableUnifiedAlerting: true,
 			DisableAnonymous:      true,
 			AppModeProduction:     true,
-			EnableFeatureToggles:  []string{"alertingConversionAPI"},
+			EnableFeatureToggles:  []string{"alertingConversionAPI", "grafanaManagedRecordingRulesDatasources", "grafanaManagedRecordingRules"},
+			EnableRecordingRules:  true,
 		})
 
 		grafanaListedAddr, env := testinfra.StartGrafanaEnv(t, dir, gpath)
@@ -392,7 +395,8 @@ func TestIntegrationConvertPrometheusEndpoints_CreatePausedRules(t *testing.T) {
 			EnableUnifiedAlerting: true,
 			DisableAnonymous:      true,
 			AppModeProduction:     true,
-			EnableFeatureToggles:  []string{"alertingConversionAPI"},
+			EnableFeatureToggles:  []string{"alertingConversionAPI", "grafanaManagedRecordingRulesDatasources", "grafanaManagedRecordingRules"},
+			EnableRecordingRules:  true,
 		})
 
 		grafanaListedAddr, env := testinfra.StartGrafanaEnv(t, dir, path)
@@ -507,7 +511,8 @@ func TestIntegrationConvertPrometheusEndpoints_FolderUIDHeader(t *testing.T) {
 			EnableUnifiedAlerting: true,
 			DisableAnonymous:      true,
 			AppModeProduction:     true,
-			EnableFeatureToggles:  []string{"alertingConversionAPI"},
+			EnableFeatureToggles:  []string{"alertingConversionAPI", "grafanaManagedRecordingRulesDatasources", "grafanaManagedRecordingRules"},
+			EnableRecordingRules:  true,
 		})
 
 		grafanaListedAddr, env := testinfra.StartGrafanaEnv(t, dir, path)
@@ -608,7 +613,8 @@ func TestIntegrationConvertPrometheusEndpoints_Delete(t *testing.T) {
 			EnableUnifiedAlerting: true,
 			DisableAnonymous:      true,
 			AppModeProduction:     true,
-			EnableFeatureToggles:  []string{"alertingConversionAPI"},
+			EnableFeatureToggles:  []string{"alertingConversionAPI", "grafanaManagedRecordingRulesDatasources", "grafanaManagedRecordingRules"},
+			EnableRecordingRules:  true,
 		})
 
 		grafanaListedAddr, env := testinfra.StartGrafanaEnv(t, dir, gpath)