refactor: stop the logging module from being responsible for fatal

# Summary

When we moved from logr to slog in #14644 we retained the ability for the logger to and exit(1) (fatal) from the legacy code. This was done for making the PR easier to digest.

This is really not the responsiblity of the logger.

Lets remove `WithFatal` from Logger in `/util/logging/logging.go that and replace each call to logger which used it with a call to os.Exit(1) afterwards.

Acceptance criteria:
* WithFatal is gone from logging.go and all implementations of the logger
* Structural support for the flag (the withFatal flag) is gone.
* No tests except for /util/logging are changed
* Nothing much else changes

## Use Cases

This is just a code improvement.

Start in /util/logging/logging.go, then search the repository for WithFatal, withFatal, and all logger implementations and call sites. Remove the logger-owned fatal support, preserve the existing behavior at callers with os.Exit(1), and verify that only /util/logging tests need changes and the acceptance criteria are met.

Written by the indexing model from the issue text.