Support for stable MSC3824

[hughns]

Depends on matrix-org/matrix-ios-sdk#1917.

Fixes #7925

n.b. this still doesn't implement the SSO redirect parameter as described for MSC3824:

• append action=login and action=register parameters to the SSO redirect URLs

Pull Request Checklist

• I read the contributing guide
• UI change has been tested on both light and dark themes, in portrait and landscape orientations and on iPhone and iPad simulators
• Accessibility has been taken into account.

• Pull request is based on the develop branch

• Pull request contains a changelog file in ./changelog.d
• You've made a self review of your PR
• Pull request includes screenshots or videos of UI changes
• Pull request includes a sign off

[pixlwave]

Makes sense to me 👍

[pixlwave]

Ah but will need a changelog of course :)

[codecov]

Codecov Report

❌ Patch coverage is 8.33333% with 11 lines in your changes missing coverage. Please review.
✅ Project coverage is 16.97%. Comparing base (ede2db6) to head (4ea0e5f).
⚠️ Report is 4 commits behind head on develop.

Files with missing lines	Patch %	Lines
Riot/Modules/Settings/SettingsViewController.m	0.00%	3 Missing ⚠️
...ions/Coordinator/UserSessionsFlowCoordinator.swift	0.00%	3 Missing ⚠️
...curity/ManageSession/ManageSessionViewController.m	0.00%	2 Missing ⚠️
...mmon/Service/MatrixSDK/AuthenticationService.swift	33.33%	1 Missing and 1 partial ⚠️
.../Coordinator/UserSessionsOverviewCoordinator.swift	0.00%	1 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff            @@
##           develop    #7991   +/-   ##
========================================
  Coverage    16.96%   16.97%           
========================================
  Files         1766     1766           
  Lines       122112   122110    -2     
  Branches     49184    49183    -1     
========================================
+ Hits         20719    20726    +7     
+ Misses      100717   100710    -7     
+ Partials       676      674    -2     

Flag	Coverage Δ
unittests	8.82% <8.33%> (+<0.01%)	⬆️

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[pixlwave]

I've also included a small fix for the sunset banners in here too (I guess something else changed in the configuration between now and when we tested these against beta.matrix.org).

And there's a fix for the UI tests in #7994.