Previously, background pre-init was started in response to the
application starting event. This meant that it would be running while
the logging turbo filter was in place and was rejecting all logging.
As a result, any logging performed during pre-init would be lost.

This commit changes background pre-init so that it is now started
in response to the application environment prepared event. By this
point, the logging turbo filter has been removed as the logging levels
have been configured from the environment.

Closes gh-21897