Add RETURNING to INSERT

Please add a RETURNING option to INSERT.

Example from PostgreSQL

postgres=# CREATE TABLE t1 (id SERIAL, name VARCHAR(100));

CREATE TABLE

postgres=# INSERT INTO t1(name) VALUES('test') RETURNING id;

 id 

----

  1

(1 row)

INSERT 0 1

Inspired by: https://evertpot.com/writing-sql-for-postgres-mysql-sqlite/

This could make it easier to write statements which work with both MariaDB and PostgreSQL. And this might improve compatibility with Oracle RDBMS.

How it'll work:

• All variants of INSERT will work — INSERT ... VALUES, INSERT ... SET, INSERT ... SELECT
• INSERT ... ON DUPLICATE KEY UPDATE will work, will return the final row values (inserted or updated)
• REPLACE will return what's inserted
• INSERT IGNORE will return what it'll try to insert, (ignoring insert errors, as expected)
• INSERT DELAYED will, obviously, not work
• rows will be returned as they're being inserted. If the insert fails in the middle and is rolled back — rows might've been sent that didn't end up in the table