fix: 4304 - save images as async instead of isolate (fallback)

[monsieurtanuki]

What

• We use isolates when we save images.
• As part of Seldom I can't take a picture #4304, we now try to save images with standard async methods, as a fallback if it failed with isolates.
• Not really sure if it makes sense, as for the moment we don't really know what goes wrong when it goes wrong (could be the isolate part, could be the save image part). We'll know better once we get Sentry messages (cf. feat: Better support error when saving the picture locally  #4305).

Part of

• Seldom I can't take a picture #4304

[codecov-commenter]

Codecov Report

Merging #4323 (72d9f3a) into develop (7487b72) will decrease coverage by 0.01%.
The diff coverage is 0.00%.

@@             Coverage Diff             @@
##           develop    #4323      +/-   ##
===========================================
- Coverage    10.81%   10.81%   -0.01%     
===========================================
  Files          287      287              
  Lines        14216    14218       +2     
===========================================
  Hits          1538     1538              
- Misses       12678    12680       +2     

Impacted Files	Coverage Δ
...mooth_app/lib/helpers/image_compute_container.dart	0.00% <0.00%> (ø)

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[github-actions]

You can test this PR on: https://app.waldo.com/applications/app-19d476740ba1bb36/sessions

[g123k]

Let's check if with our two fixes it will happen again… or not 🤞