LastImportTime for resource. (#112153)

* LastImportTime for resource.

* Make StorageBackendImpl implement GetResourceLastImportTimes

* More missing implementations of GetResourceLastImportTimes

* Fix import.

* Skip TestGetResourceLastImportTime in TestBadgerKVStorageBackend.

* Implement GetResourceLastImportTimes by mockStorageBackend

* Bump test tolerance.

* Fix postgres query and timezone.

* Fix postgres query and timezone.

* Make linter happy.

pkg/storage/unified/sql/testdata/mysql--resource_last_import_time_insert-insert.sql

@@ -0,0 +1,12 @@
+  INSERT INTO `resource_last_import_time` (
+      `group`,
+      `resource`,
+      `namespace`,
+      `last_import_time`
+    ) VALUES (
+      'group',
+      'res',
+      'ns',
+      '2025-10-07 22:30:05 +0000 UTC'
+    ) ON DUPLICATE KEY UPDATE `last_import_time` = '2025-10-07 22:30:05 +0000 UTC'
+;

pkg/storage/unified/sql/testdata/mysql--resource_last_import_time_query-insert.sql

@@ -0,0 +1,8 @@
+SELECT
+  `namespace`,
+  `group`,
+  `resource`,
+  `last_import_time`
+FROM
+  `resource_last_import_time`
+;

pkg/storage/unified/sql/testdata/postgres--resource_last_import_time_insert-insert.sql

@@ -0,0 +1,13 @@
+    INSERT INTO "resource_last_import_time" (
+       "group",
+       "resource",
+       "namespace",
+       "last_import_time"
+     ) VALUES (
+       'group',
+       'res',
+       'ns',
+       '2025-10-07 22:30:05 +0000 UTC'
+    ) ON CONFLICT ("group", "resource", "namespace")
+      DO UPDATE SET "last_import_time" = '2025-10-07 22:30:05 +0000 UTC'
+;

pkg/storage/unified/sql/testdata/postgres--resource_last_import_time_query-insert.sql

@@ -0,0 +1,8 @@
+SELECT
+  "namespace",
+  "group",
+  "resource",
+  "last_import_time"
+FROM
+  "resource_last_import_time"
+;

pkg/storage/unified/sql/testdata/sqlite--resource_last_import_time_insert-insert.sql

@@ -0,0 +1,12 @@
+   INSERT OR REPLACE INTO "resource_last_import_time" (
+       "group",
+       "resource",
+       "namespace",
+       "last_import_time"
+   ) VALUES (
+       'group',
+       'res',
+       'ns',
+       '2025-10-07 22:30:05 +0000 UTC'
+   )
+;

pkg/storage/unified/sql/testdata/sqlite--resource_last_import_time_query-insert.sql

@@ -0,0 +1,8 @@
+SELECT
+  "namespace",
+  "group",
+  "resource",
+  "last_import_time"
+FROM
+  "resource_last_import_time"
+;