feat: generate PgSqlState.java from errcodes.txt

[jorsol]

This is an ad hoc hack around generate-errcodes.pl to create the PgSqlState.java class, which creates a full list of the error codes found in errcodes.txt from the postgresql server.

It's a class with String constants since having an enum version its useless, the idea would be to start using this version and slowly changing all the usage of PSQLState until it can be removed.

This PR change the Parser to throw SQLSyntaxErrorException with the PgSqlState code, a refactor for other parts of the code could follow later.

closes: #534
relates to: #963

[vlsi]

@jorsol , thanks for taking time to implemet this.

However, I'm inclined to tentatively decline Perl script (which requires Perl installed) in favour of Kotlin script (which is bundled with Gradle).

PS. It would really help if you could review and/or try #1627

[jorsol]

The perl script was just a hack around the script that the server uses, but I also think would be a better alternative to use a Kotlin/Gradle script, I'm not familiar with either Gradle or Kotlin, but I will try to find some space to review the migration to Gradle.