Writes the GUI settings to `guisettings.bak` in the data directory
before wiping them. This can be used to retroactively troubleshoot
issues (e.g. #11262) where `-resetguisettings` solves the problem.
Github-Pull: #11338
Rebased-From: 723aa1b8752c1d6c6c0a76059c532ebe2f406fc1