feat: create backend routes and API for importing saved queries (#13893)

* initial commit

* revisions

* started tests

* added unit tests

* revisions

* tests passing

* fixed api test

* Update superset/queries/saved_queries/commands/importers/v1/utils.py

Co-authored-by: Hugh A. Miles II <hughmil3s@gmail.com>

* Revert "Update superset/queries/saved_queries/commands/importers/v1/utils.py"

This reverts commit 18580aad1e.

Co-authored-by: Hugh A. Miles II <hughmil3s@gmail.com>

tests/fixtures/importexport.py

@@ -343,7 +343,11 @@ dashboard_metadata_config: Dict[str, Any] = {
     "type": "Dashboard",
     "timestamp": "2020-11-04T21:27:44.423819+00:00",
 }
-
+saved_queries_metadata_config: Dict[str, Any] = {
+    "version": "1.0.0",
+    "type": "SavedQuery",
+    "timestamp": "2021-03-30T20:37:54.791187+00:00",
+}
 database_config: Dict[str, Any] = {
     "allow_csv_upload": True,
     "allow_ctas": True,
@@ -499,3 +503,12 @@ dashboard_config = {
     },
     "version": "1.0.0",
 }
+saved_queries_config = {
+    "schema": "public",
+    "label": "Test Saved Query",
+    "description": None,
+    "sql": "-- Note: Unless you save your query, these tabs will NOT persist if you clear\nyour cookies or change browsers.\n\n\nSELECT * from birth_names",
+    "uuid": "05b679b5-8eaf-452c-b874-a7a774cfa4e9",
+    "version": "1.0.0",
+    "database_uuid": "b8a1ccd3-779d-4ab7-8ad8-9ab119d7fe89",
+}