Fixes #35420 - Drop boot_settings.rb for early settings

With Rails 7 require_relative no longer works in a Gemfile (maybe it's
Zeitwerk?). Currently we only support Rails 6.1 anyway and if we can't
use the mechanism for Rails 7 this mechanism should be removed.

An environment variable has been considered but in testing the
environment variable was not passed on and issues with the lockfile
showed up.

When we upgrade Rails to 7.0 a new mechnism needs to be found.