Add pgx/v5 and set isolation to serializable level

Following this comment: #862 (comment)

And reference PR:
https://github.com/golang-migrate/migrate/pull/656/files

Author: sizengyu-spgroup

database/pgx/pgx.go

@@ -447,7 +447,7 @@ func runesLastIndex(input []rune, target rune) int {
 }
 
 func (p *Postgres) SetVersion(version int, dirty bool) error {
-	tx, err := p.conn.BeginTx(context.Background(), &sql.TxOptions{})
+	tx, err := p.conn.BeginTx(context.Background(), &sql.TxOptions{Isolation: sql.LevelSerializable})
 	if err != nil {
 		return &database.Error{OrigErr: err, Err: "transaction start failed"}
 	}

database/pgx/v5/pgx.go

@@ -338,12 +338,12 @@ func runesLastIndex(input []rune, target rune) int {
 }
 
 func (p *Postgres) SetVersion(version int, dirty bool) error {
-	tx, err := p.conn.BeginTx(context.Background(), &sql.TxOptions{})
+	tx, err := p.conn.BeginTx(context.Background(), &sql.TxOptions{Isolation: sql.LevelSerializable})
 	if err != nil {
 		return &database.Error{OrigErr: err, Err: "transaction start failed"}
 	}
 
-	query := `TRUNCATE ` + quoteIdentifier(p.config.migrationsSchemaName) + `.` + quoteIdentifier(p.config.migrationsTableName)
+	query := `DELETE FROM ` + quoteIdentifier(p.config.migrationsSchemaName) + `.` + quoteIdentifier(p.config.migrationsTableName)
 	if _, err := tx.Exec(query); err != nil {
 		if errRollback := tx.Rollback(); errRollback != nil {
 			err = multierror.Append(err, errRollback)