Storage/SQL: Support more filter by namespace/group/resource (#99249)

pkg/storage/unified/sql/testdata/mysql--resource_stats-resource.sql

@@ -0,0 +1,16 @@
+SELECT
+  `namespace`,
+  `group`,
+  `resource`,
+  COUNT(*),
+  MAX(`resource_version`)
+FROM `resource`
+WHERE 1 = 1
+  AND `namespace` = 'default'
+  AND `group` = 'dashboard.grafana.app'
+  AND `resource` = 'dashboards'
+GROUP BY 
+  `namespace`,
+  `group`,
+  `resource`
+;