[TASK] Cleanup ext:sv

* Remove old class files
* Move image and language files to ExtBase structure
* Delete unused CSS file

Change-Id: Icbf13d62397f0f5a1eb2bcccd76e9b81541d27b1
Resolves: #51593
Releases: 6.2
Reviewed-on: https://review.typo3.org/23481
Reviewed-by: Kai Ole Hartwig
Tested-by: Kai Ole Hartwig
Reviewed-by: Christian Kuhn
Tested-by: Christian Kuhn