fix: schema cache retrying without backoff

Fixes https://github.com/PostgREST/postgrest/issues/3523.

Now if there's a failure when obtaining the pg version OR schema cache,
we do the same retrying process. This way we don't add two retries.

Refactors and renames the "connectionWorker" to "schemaCacheLoader".
This makes more sense since what we really want is the schema cache,
the version is the pre-requisite for ensuring our
schema cache queries work.

Additionally, we no longer log ` Attempting to connect to the database...`
at startup unnecessarily. This is only logged whenever there's a retry attempt.

CHANGELOG.md

@@ -11,6 +11,7 @@ This project adheres to [Semantic Versioning](http://semver.org/).
  - #3644, Make --dump-schema work with in-database pgrst.db_schemas setting - @wolfgangwalther
  - #3644, Show number of timezones in schema cache load report - @wolfgangwalther
  - #3644, List correct enum options in OpenApi output when multiple types with same name are present - @wolfgangwalther
+ - #3523, Fix schema cache loading retry without backoff - @steve-chavez
 
 ## [12.2.1] - 2024-06-27