sql: Implement AUTOINCREMENT feature for int PKs

Implement support for AUTOINCREMENT feature for integer
primary keys of tables which lack rowid property.
All tables which live in Tarantool's universe are lack
rowid.
To implement it two new op-codes were introduced:
  - Fetch maximum integer value of given space/index/fieldno
  - Copy register content from top frame into current frame

Convert AUTOINCREMENT test coverage: sql-tap/autoinc.test

Closes #2263