[test_youtube_signatures] Modernize
Regroup and hide workaround options

These options are rarely necessary. Hide them to make the important options in the general group more obvious.
Group cache-related options under filesystem
Reorder filesytem options

* Push down the deprecated ones
* Roughly order file-name, no-*, write-*, further options
deprecate --title

This is the default already. If you want a specific format, pick it with -o or --id.
Add --rm-cache-dir