[FEATURE] High-res TYPO3 logo in topbar

Allow hi-res logo in TYPO3 backend topbar.
Automatically scales when @2x in filename is detected.

Change-Id: I17044b909e11c3efa1ab2e13bda1b9cf1ac9624e
Resolves: #52514
Releases: 6.2
Reviewed-on: https://review.typo3.org/24340
Reviewed-by: Xavier Perseguers
Tested-by: Xavier Perseguers
Reviewed-by: Philipp Gampe
Tested-by: Philipp Gampe