Let the SDK retrieve and parse Element well known content

[bmarty]

Type of change

• Feature
• Bugfix
• Technical
• Other :

Content

Configure Element Call's widget URL using the new SDK APIs that perform HTTP request and parses the element.json wellknown

FTR iOS PR is element-hq/element-x-ios#2971

Motivation and context

Closes #3124

Screenshots / GIFs

Tests

• Not tested with a server having custom configuration, but this should not break doing a call using matrix.org for instance.

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

Attention: Patch coverage is 75.00000% with 2 lines in your changes missing coverage. Please review.

Project coverage is 76.00%. Comparing base (b46f47f) to head (3135c53).
Report is 5 commits behind head on develop.

Files	Patch %	Lines
.../android/libraries/matrix/test/FakeMatrixClient.kt	50.00%	2 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff             @@
##           develop    #3127      +/-   ##
===========================================
+ Coverage    75.96%   76.00%   +0.04%     
===========================================
  Files         1638     1636       -2     
  Lines        38629    38590      -39     
  Branches      7465     7459       -6     
===========================================
- Hits         29344    29332      -12     
+ Misses        5397     5371      -26     
+ Partials      3888     3887       -1     

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