refactor: replace specific extractor implementations with a generic extractor; remove mssql and postgres extractor files

cmd/go_migrate/process.go

@@ -39,7 +39,7 @@ func processMigrationJob(
 	targetDbWrapper dbwrapper.DbWrapper,
 	sourceTableAnalyzer etl.TableAnalyzer,
 	targetTableAnalyzer etl.TableAnalyzer,
-	extractor etl.Extractor,
+	extractor extractors.GenericExtractor,
 	azureClient *azure.Client,
 	loader etl.Loader,
 	job config.Job,
@@ -155,9 +155,8 @@ func processMigrationJob(
 
 	for range maxExtractors {
 		wgExtractors.Go(func() {
-			extractors.Consume(
+			extractor.Consume(
 				localCtx,
-				extractor,
 				job.SourceTable,
 				sourceColTypes,
 				job.BatchSize,