go.mod: update pg_query_go/v4 to v4.2.3

Fixes pganalyze/pg_query_go#95

generate StringPtr for Null* enums

add invalid enum values, reduce line noise

generate enum stringers

add more codegen support for nullables

fix Go struct tag parsing

304ba5d didn't correctly handle struct tags whose
value contained a space. (My fault.)

Use a proper struct tag library with a dedicated parser
that handles all the edge cases. Less code, and better.

i'm the captain now

release(cmd/sqlc): Bump to v1.13.0 (sqlc-dev#1523)

* release(cmd/sqlc): Bump version to v1.13.0

* chore: Regenerate test data with latest version

* release: Update download links

* docs: Update the changelog

cmd/sqlc: Bump version to v1.12.0 (sqlc-dev#1415)

* docs: Add v1.12.0 to the Changelog

cmd/sqlc: Bump version to v1.11.0