Clean up iOS 14 availability checks

[Johennes]

Now that the minimum deployment target is iOS 14, we can remove a bunch of availability checks. This PR contains two commits.

The first commit removes all @available(iOS 14.... This was done with a regex replace.

The second commit expands ifs and guards that involved @available(iOS 14... or #available(iOS 14.... This one I have done by hand so you probably want to look at it more closely.

Note that there are still availability checks pre-iOS14 left. I haven't touched those to note make this PR bigger than it already is.

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

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[codecov-commenter]

Codecov Report

Merging #6333 (f1d8e80) into develop (8927bff) will increase coverage by 0.00%.
The diff coverage is 13.86%.

@@            Coverage Diff            @@
##           develop    #6333    +/-   ##
=========================================
  Coverage     6.17%    6.17%            
=========================================
  Files         1440     1440            
  Lines       155408   155099   -309     
  Branches     62521    62360   -161     
=========================================
- Hits          9592     9584     -8     
+ Misses      145413   145112   -301     
  Partials       403      403            

Impacted Files	Coverage Δ
Config/BuildSettings.swift	42.18% <ø> (+4.15%)	⬆️
Riot/Categories/Publisher+Riot.swift	66.66% <ø> (ø)
...t/Managers/UISIAutoReporter/UISIAutoReporter.swift	20.75% <ø> (ø)
...dules/Common/SwiftUI/VectorHostingController.swift	80.00% <ø> (ø)
...ntextMenu/ActionProviders/RoomActionProvider.swift	0.00% <0.00%> (ø)
...iot/Modules/CreateRoom/CreateRoomCoordinator.swift	0.00% <0.00%> (ø)
...t/Modules/MediaPickerV2/MediaPickerPresenter.swift	0.00% <ø> (ø)
Riot/Modules/Room/RoomCoordinator.swift	0.00% <0.00%> (ø)
...Modules/Room/Settings/RoomSettingsViewController.m	0.00% <0.00%> (ø)
...tyles/Plain/Cells/Location/LocationPlainCell.swift	0.00% <0.00%> (ø)
... and 211 more

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[Johennes]

@pixlwave / @ismailgulek I assigned you manually as reviewers because you seem to be around and this week might be a good one to get this large diff landed. 😅

[pixlwave]

Thanks for doing this Johennes (and for splitting it up into smaller commits 🙏).

Looks good to me!

[ismailgulek]

LGTM!
I hope there is not a fork who wants to support pre iOS 14 :)