[stable-3.10] Show more informative error message when VFS hydration fails. Displaya popup and put an error into activity list. More detailed logs.

[backportbot-nextcloud]

Backport of #6140

[nextcloud-desktop-bot]

AppImage file: nextcloud-PR-6153-dd1946604f93b19d39b67087365376989a02e869-x86_64.AppImage

To test this change/fix you can simply download above AppImage file and test it.

Please make sure to quit your existing Nextcloud app and backup your data.

[sonarqubecloud]

SonarCloud Quality Gate failed.   

0 Bugs
0 Vulnerabilities
0 Security Hotspots
8 Code Smells

3.8% Coverage
0.0% Duplication

Catch issues before they fail your Quality Gate with our IDE extension SonarLint

[codecov]

Codecov Report

Merging #6153 (dd19466) into stable-3.10 (3392933) will increase coverage by 0.09%.
Report is 2 commits behind head on stable-3.10.
The diff coverage is 88.88%.

Additional details and impacted files

@@               Coverage Diff               @@
##           stable-3.10    #6153      +/-   ##
===============================================
+ Coverage        60.54%   60.63%   +0.09%     
===============================================
  Files              145      145              
  Lines            18807    18822      +15     
===============================================
+ Hits             11386    11413      +27     
+ Misses            7421     7409      -12     

Files	Coverage Δ
src/common/vfs.h	52.38% <ø> (ø)
src/libsync/vfs/cfapi/hydrationjob.h	0.00% <ø> (ø)
src/libsync/vfs/cfapi/vfs_cfapi.cpp	84.52% <100.00%> (+0.11%)	⬆️
src/libsync/vfs/cfapi/hydrationjob.cpp	53.65% <87.50%> (+2.09%)	⬆️

... and 6 files with indirect coverage changes