[stable12] Use PNG icons for activity emails and ios client

[nickvergessen]

Backport #5483

• Activity app PR: [stable12] Use PNG icons for emails and ios client activity#176

[MorrisJobke]

Tested and works 👍

[ArtificialOwl]

This was yesterday on master

---

This is today on stable12

[ArtificialOwl]

looks like an issue with the webmail client, original mail on the server contains the right img src=""

[codecov]

Codecov Report

Merging #5648 into stable12 will decrease coverage by 0.13%.
The diff coverage is 4.71%.

@@              Coverage Diff               @@
##             stable12    #5648      +/-   ##
==============================================
- Coverage       54.19%   54.05%   -0.14%     
- Complexity      22358    22442      +84     
==============================================
  Files            1379     1379              
  Lines           85556    85769     +213     
  Branches         1329     1329              
==============================================
+ Hits            46363    46365       +2     
- Misses          39193    39404     +211

Impacted Files	Coverage Δ	Complexity Δ
...es_sharing/lib/Activity/Providers/RemoteShares.php	0% <0%> (ø)	17 <0> (+2)	⬆️
...files_sharing/lib/Activity/Providers/Downloads.php	0% <0%> (ø)	17 <0> (+2)	⬆️
...pps/files_sharing/lib/Activity/Providers/Users.php	0% <0%> (ø)	23 <0> (+2)	⬆️
apps/dav/lib/CalDAV/Activity/Provider/Todo.php	0% <0%> (ø)	25 <0> (+1)	⬆️
apps/files/lib/Activity/FavoriteProvider.php	0% <0%> (ø)	18 <0> (+4)	⬆️
apps/files/lib/Activity/Provider.php	13.69% <0%> (-3.85%)	71 <0> (+16)
apps/systemtags/lib/Activity/Provider.php	0% <0%> (ø)	41 <0> (+2)	⬆️
apps/sharebymail/lib/Activity.php	0% <0%> (ø)	39 <0> (+8)	⬆️
...ps/files_sharing/lib/Activity/Providers/Groups.php	0% <0%> (ø)	17 <0> (+2)	⬆️
apps/comments/lib/Activity/Provider.php	5.82% <0%> (-0.18%)	22 <0> (+1)
... and 11 more