Display errors raised during account edit

[RiccardoM]

Description

Implemented the showing of errors that are raised during the edit of the account (fixes #26)

Checklist

• [x] Targeted PR against correct branch.
• [x] Linked to Github issue with discussion and accepted design OR link to spec that describes this work.
• [x] Wrote unit tests.
• [x] Run flutter format.
• [ ] Updated the documentation.
• [ ] Added an entry to the CHANGELOG.md file.
• [ ] Re-reviewed Files changed in the Github PR explorer.

[codecov[bot]]

Codecov Report

Merging #52 into master will decrease coverage by 0.04%. The diff coverage is 12.50%.

@@            Coverage Diff             @@
##           master      #52      +/-   ##
==========================================
- Coverage   18.14%   18.10%   -0.05%     
==========================================
  Files         245      247       +2     
  Lines        5963     6027      +64     
==========================================
+ Hits         1082     1091       +9     
- Misses       4881     4936      +55     

Impacted Files	Coverage Δ
...b/sources/user/remote/remote_user_source_impl.dart	33.33% <0.00%> (-3.04%)	:arrow_down:
lib/ui/blocs/account/edit/edit_account_bloc.dart	0.00% <0.00%> (ø)
lib/ui/blocs/account/edit/edit_account_event.dart	0.00% <0.00%> (ø)
lib/ui/blocs/account/edit/edit_account_state.dart	0.00% <0.00%> (ø)
lib/ui/localization/export.dart	0.00% <0.00%> (ø)
lib/ui/screens/post_create_screen.dart	0.00% <ø> (ø)
lib/ui/widgets/account/edit/accont_edit_body.dart	0.00% <0.00%> (ø)
...widgets/account/edit/account_edit_error_popup.dart	0.00% <0.00%> (ø)
lib/ui/widgets/account/edit/image_picker.dart	0.00% <0.00%> (ø)
lib/ui/widgets/login/popups/login_popup.dart	0.00% <0.00%> (ø)
... and 8 more

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