Meta: Issues found with iOS 15 build on XCode 13

[langleyd]

Issues found

• Navigation bars appear transparent on some modal screens. #4884
• Extra spacing is inserted before the headers in HomeViewController. #4941
• Sometimes space icons are zoomed in #5177 (specifically the home space icon)
• Adopt the new tab bar style when scrolled to the bottom of a list.
• The tab bar badges don't update automatically. #5421 Existed with Xcode 12.
• Long pressing on an avatar on the Home tab jumps back to the start of the collection view
• Media library causes freezes under iOS 15.2 #5465

Other tasks

• Update Fastfile for CI
• Check for any updates needed in the MatrixSDK repo (probably just CI)