[Bugfix] : fix self verification flow

[ganfra]

Content

This PR solves 2 things :

• There were race condition in the creation of the verificationController so nothing would work in those cases.
• Cancellation of verification wasn't correctly done in some cases

Motivation and context

Closes #3418

Screenshots / GIFs

Tests

• Step 1
• Step 2
• Step ...

Tested devices

• Physical
• Emulator
• OS version(s):

Checklist

• Changes have been tested on an Android device or Android emulator with API 23
• UI change has been tested on both light and dark themes
• Accessibility has been taken into account. See https://github.com/element-hq/element-x-android/blob/develop/CONTRIBUTING.md#accessibility
• Pull request is based on the develop branch
• Pull request title will be used in the release note, it clearly define what will change for the user
• Pull request includes screenshots or videos if containing UI changes
• Pull request includes a sign off
• You've made a self review of your PR

[github-actions]

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[sonarcloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarCloud

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 82.65%. Comparing base (fc0bb64) to head (a7ab8ee).
Report is 3 commits behind head on develop.

Additional details and impacted files

@@           Coverage Diff            @@
##           develop    #3426   +/-   ##
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  Coverage    82.65%   82.65%           
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  Files         1705     1705           
  Lines        40076    40076           
  Branches      4881     4881           
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  Hits         33125    33125           
  Misses        5233     5233           
  Partials      1718     1718           

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[jmartinesp]

The code LGTM and I confirm it fixes the issue, thanks!