Public page template enhancements

[juliusknorr]

• Move common menu templates from the files_sharing app to public API
• Add footer to all public pages
• Some cleanup of public page styles (moving them out of the files_sharing app)

required for nextcloud/gallery#425

[codecov]

Codecov Report

Merging #9084 into master will decrease coverage by 0.07%.
The diff coverage is 22.58%.

@@             Coverage Diff              @@
##             master    #9084      +/-   ##
============================================
- Coverage     51.96%   51.89%   -0.08%     
- Complexity    25287    25289       +2     
============================================
  Files          1601     1601              
  Lines         94978    94981       +3     
  Branches       1388     1388              
============================================
- Hits          49360    49294      -66     
- Misses        45618    45687      +69

Impacted Files	Coverage Δ	Complexity Δ
...es_sharing/composer/composer/autoload_classmap.php	0% <ø> (ø)	0 <0> (ø)	⬇️
...blic/AppFramework/Http/Template/LinkMenuAction.php	14.28% <ø> (ø)	2 <0> (?)
...iles_sharing/composer/composer/autoload_static.php	0% <ø> (ø)	1 <0> (ø)	⬇️
...s/files_sharing/lib/Controller/ShareController.php	47.38% <ø> (ø)	64 <0> (ø)	⬇️
apps/files_sharing/templates/public.php	0% <0%> (ø)	0 <0> (ø)	⬇️
core/templates/layout.public.php	0% <0%> (ø)	0 <0> (ø)	⬇️
...Framework/Http/Template/PublicTemplateResponse.php	67.56% <0%> (-8.2%)	16 <2> (+2)
...ramework/Http/Template/ExternalShareMenuAction.php	31.25% <0%> (ø)	2 <0> (?)
apps/files_sharing/js/public.js	47.91% <0%> (-0.83%)	0 <0> (ø)
core/js/public/publicpage.js	66.66% <70%> (-8.34%)	0 <0> (ø)
... and 5 more

[MorrisJobke]

Tested and works 👍