Support for require_auth configuration parameter

**Is your feature request related to a problem? Please describe.**
Postgres 16 added a new configuration parameter named _require_auth_:

[PostgreSQL: pgsql: libpq: Add support for require_auth to control authorized auth m](https://www.postgresql.org/message-id/E1pbwmD-003Rqr-6b%40gemulon.postgresql.org)

There's also an environment variable: PGREQUIREAUTH

Could it be that pgx does not handle this yet?

**Describe the solution you'd like**
Support for use of require_auth in the database connect URI.

**Describe alternatives you've considered**
None known.
**Additional context**
Feature documentation: https://www.postgresql.org/docs/16/libpq-connect.html#LIBPQ-CONNECT-REQUIRE-AUTH

No source file or test is named. Start by locating pgx's database connect-URI parsing and configuration handling, then compare the PostgreSQL 16 require_auth and PGREQUIREAUTH behavior described in the linked PostgreSQL documentation. Done means require_auth can be supplied through the database connect URI with coverage for the supported behavior.

Written by the indexing model from the issue text.