Refactor/remove splash

[bdmendes]

Closes #850
This refactors the initial route logic, making it immediately the login or the home screen depending on the saved info state. Also tweaks offline image storage to trigger a login if a new request is needed.

Review checklist

• Terms and conditions reflect the current change
• Contains enough appropriate tests
• If aimed at production, writes a new summary in whatsnew/whatsnew-pt-PT
• Properly adds an entry in changelog.md with the change
• If PR includes UI updates/additions, its description has screenshots
• Behavior is as expected
• Clean, well-structured code

[codecov]

Codecov Report

Merging #919 (b051cf9) into develop (77631b1) will decrease coverage by 10.28%.
Report is 2 commits behind head on develop.
The diff coverage is 10.00%.

Additional details and impacted files

@@             Coverage Diff              @@
##           develop     #919       +/-   ##
============================================
- Coverage    31.47%   21.20%   -10.28%     
============================================
  Files           81      136       +55     
  Lines         2364     3514     +1150     
============================================
+ Hits           744      745        +1     
- Misses        1620     2769     +1149     

Files Changed	Coverage Δ
uni/lib/controller/cleanup.dart	0.00% <0.00%> (ø)
...controller/local_storage/file_offline_storage.dart	19.04% <0.00%> (-4.49%)	⬇️
uni/lib/controller/networking/network_router.dart	24.13% <0.00%> (ø)
uni/lib/model/entities/exam.dart	54.83% <0.00%> (ø)
.../lib/model/providers/startup/profile_provider.dart	7.89% <0.00%> (-2.50%)	⬇️
.../lib/model/providers/startup/session_provider.dart	0.00% <0.00%> (ø)
...i/lib/model/providers/state_provider_notifier.dart	20.00% <ø> (ø)
uni/lib/utils/drawer_items.dart	0.00% <0.00%> (ø)
uni/lib/view/navigation_service.dart	0.00% <0.00%> (ø)
.../common_widgets/pages_layouts/general/general.dart	70.00% <75.00%> (+1.03%)	⬆️

... and 56 files with indirect coverage changes

[LuisDuarte1]

LGTM, nice job 🚀

[thePeras]

Working in IOS really nice!