Cleanup old entries from resource_last_import_time table. (#112438)

* Cleanup old entries from resource_last_import_time table.

* Add index for last_import_time column.

* Address review feedback.

pkg/storage/unified/sql/queries.go

@@ -61,6 +61,7 @@ var (
 
 	sqlResourceLastImportTimeInsert = mustTemplate("resource_last_import_time_insert.sql")
 	sqlResourceLastImportTimeQuery  = mustTemplate("resource_last_import_time_query.sql")
+	sqlResourceLastImportTimeDelete = mustTemplate("resource_last_import_time_delete.sql")
 )
 
 // TxOptions.
@@ -489,3 +490,12 @@ type sqlResourceLastImportTimeQueryRequest struct {
 func (r *sqlResourceLastImportTimeQueryRequest) Validate() error {
 	return nil
 }
+
+type sqlResourceLastImportTimeDeleteRequest struct {
+	sqltemplate.SQLTemplate
+	Threshold time.Time
+}
+
+func (r *sqlResourceLastImportTimeDeleteRequest) Validate() error {
+	return nil
+}