feat: add extract query builders for both dialects

Add QueryFromObject helpers to build select queries from a table schema, with limits and geometry support.

cmd/go_migrate/main.go

@@ -5,25 +5,17 @@ import (
 )
 
 type MigrationJob struct {
-	Schema     string
-	Table      string
-	PrimaryKey string
+	Schema string
+	Table  string
 }
 
 var migrationJobs []MigrationJob = []MigrationJob{
 	{
-		Schema:     "demo",
-		Table:      "users",
-		PrimaryKey: "id",
+		Schema: "demo",
+		Table:  "users",
 	},
 }
 
-const (
-	NumExtractors int = 2
-	ChunkSize     int = 20
-	QueueSize     int = 10
-)
-
 func main() {
 	configureLog()
 	log.Info("Starting migration...")