Navigation support for upcoming Element Call Picture in Picture mode.

[pixlwave]

This PR adds the initial support for EC PiP with the following changes:

• Replace the sheet with a SwiftUI fullscreen overlay (so we can hide the web view without removing it from the view hierarchy).
• Listen for AVPictureInPictureController notifications and use these to show/hide the call overlay.
• Make sure that joining the same call that's running in PiP, dismisses the PiP instead of creates a new call.
• Dismiss the composer before starting a call (as there's no longer a sheet to take the focus away).

[github-actions]

	Warnings
⚠️	Some of the commits are missing ticket numbers. Please consider squashing all commits that don't have a tracking number.
⚠️	You seem to have made changes to views. Please consider adding screenshots.

Generated by 🚫 Danger Swift against b9fa309

[sonarcloud]

Quality Gate passed

Issues
1 New issue
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 53.42466% with 102 lines in your changes missing coverage. Please review.

Project coverage is 77.18%. Comparing base (cf35056) to head (b9fa309).
Report is 4 commits behind head on develop.

Files	Patch %	Lines
...urces/Screens/CallScreen/CallScreenViewModel.swift	0.00%	42 Missing ⚠️
...X/Sources/Screens/CallScreen/View/CallScreen.swift	0.00%	20 Missing ⚠️
.../FlowCoordinators/UserSessionFlowCoordinator.swift	0.00%	18 Missing ⚠️
...pplication/Navigation/NavigationCoordinators.swift	78.43%	11 Missing ⚠️
...ces/Screens/CallScreen/CallScreenCoordinator.swift	0.00%	5 Missing ⚠️
...ces/Screens/RoomScreen/RoomScreenCoordinator.swift	0.00%	2 Missing ⚠️
...ests/Sources/NavigationSplitCoordinatorTests.swift	97.43%	2 Missing ⚠️
...urces/Screens/RoomScreen/RoomScreenViewModel.swift	0.00%	1 Missing ⚠️
...rces/Services/ElementCall/ElementCallService.swift	0.00%	1 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff             @@
##           develop    #3174      +/-   ##
===========================================
- Coverage    77.33%   77.18%   -0.15%     
===========================================
  Files          717      717              
  Lines        56141    56501     +360     
===========================================
+ Hits         43415    43609     +194     
- Misses       12726    12892     +166     

Flag	Coverage Δ
unittests	68.37% <53.42%> (-0.09%)	⬇️

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[stefanceriu]

Nothing to comment, looks great! 👏