Support ALTER COLUMN RESTART WITH

As a replacement for the broken `sys.alter_seq_restart` stored procedure. For general, non-identity sequence changes we'll probably just want to implement ALTER SEQUENCE.

Also remove support for SET INCREMENT BY because it didn't actually work and not straight forward to do.
Yes, you can go lower than the previous value.

Defaults 1 and Long.MAX_VALUE. We don't support syntax for specifying MIN VALUE and MAX VALUE on IDENTITY (there's a card tracking that).