Refactors our use ofslogtest to instantiate a "standard logger" across most of our tests. This standard logger incorporatescoder/slog#217 to also ignore database query canceled errors by default, which are a source of low-severity flakes.

Any test that has set non-defaultslogtest.Options is left alone. In particular,coderdtest defaults to ignoring all errors. We might consider revisiting that decision now that we have better tools to target the really common flaky Error logs on shutdown.