fix(compiler): prevent schema parse failures by ignoring psql meta commands

[andrewmbenton]

This is kind of a lazy quick-and-dirty implementation that doesn't attempt to consolidate some duplicate line parsing that we do during migration removal and just sticks a func right in the package that handles file parsing for all engines, even though this line filter only applies to postgresql.

Happy to revise if there's a better place to put this.

Resolves#4065

[atombender]

Can this please be merged? It's a blocking issue with Postgres 17. @kyleconroy

[gbarr]

This seems a little aggressive to remove all lines that begin with \. The following is valid SQL, but would be broken by this fix

SELECT E'
\x61 b c
';

I don't think pg_dump would create such a statement but hand written SQL could.

I would suggest that the fix only exclude lines starting with \restrict and \unrestrict

[j-houston]

Bump. Can we get this merged?

[ignatremizov]

I added #4177 to address @gbarr comment and not to break any other existing postgresql workflows (i.e., on /connect or other psql meta commands)

[kyleconroy]

Fixed via #4390