feat: Clients should initialize MLS clients according to backend feature flag - WPB-10118

[KaterinaWire]

Issue

All clients need to register an MLS client by only doing so when the following conditions are fulfilled:

• GET /mls/public-keys contains an entry with the key removal. As a "defensive programming" we can check if there is at least one non-nil and non-empty key.
• The mls feature config is enabled (status = enabled)

The DeveloperFlag.enableMLSSupport flag should also be removed, since the source of feature status should be feature config.

Needs to release with:

• [https://github.com/wireapp/wire-ios-build-assets/pull/130]

Testing

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Checklist

• Title contains a reference JIRA issue number like [WPB-XXX].
• Description is filled and free of optional paragraphs.
• Adds/updates automated tests.

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UI accessibility checklist

If your PR includes UI changes, please utilize this checklist:

• Make sure you use the API for UI elements that support large fonts.
• All colors are taken from WireDesign.ColorTheme or constructed using WireDesign.BaseColorPalette.
• New UI elements have Accessibility strings for VoiceOver.

[github-actions]

Test Results

   11 files    976 suites   13m 17s ⏱️
7 818 tests 7 818 ✅ 0 💤 0 ❌
7 837 runs  7 837 ✅ 0 💤 0 ❌

Results for commit 75a30e0.

♻️ This comment has been updated with latest results.

[johnxnguyen]

Regarding GetMLSFeatureUseCase, it doesn't really feel like a use case to me. A use case, I would argue, is some public API for the presentation layer to invoke. Instead, getting the MLS feature config is already provided by the feature repository, so why is this extra layer needed?