Add a certificate validator hook.

[pixlwave]

This PR contains 2 commits:

• Add the new hook for use in Element Call web views (default implementation does nothing as usual).
• Exposes all the hooks for direct use (so we can have multiple methods on them), adds default implementations and tidies up AppHooks.swift into multiple files.

Probably easiest to review commit-by-commit.

[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 d00f05e

[codecov]

Codecov Report

Attention: Patch coverage is 19.04762% with 34 lines in your changes missing coverage. Please review.

Project coverage is 77.83%. Comparing base (74907d3) to head (d00f05e).

Files	Patch %	Lines
ElementX/Sources/AppHooks/AppHooks.swift	23.52%	13 Missing ⚠️
...X/Sources/Screens/CallScreen/View/CallScreen.swift	0.00%	6 Missing ⚠️
...rces/AppHooks/Hooks/CertificateValidatorHook.swift	0.00%	3 Missing ⚠️
...urces/Screens/CallScreen/CallScreenViewModel.swift	0.00%	3 Missing ⚠️
ElementX/Sources/Application/AppCoordinator.swift	0.00%	2 Missing ⚠️
.../FlowCoordinators/UserSessionFlowCoordinator.swift	33.33%	2 Missing ⚠️
...ces/Screens/CallScreen/CallScreenCoordinator.swift	0.00%	2 Missing ⚠️
...mentX/Sources/AppHooks/Hooks/AppSettingsHook.swift	0.00%	1 Missing ⚠️
...ntX/Sources/AppHooks/Hooks/ClientBuilderHook.swift	0.00%	1 Missing ⚠️
...mentX/Sources/Other/Extensions/ClientBuilder.swift	0.00%	1 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff             @@
##           develop    #3069      +/-   ##
===========================================
- Coverage    77.93%   77.83%   -0.11%     
===========================================
  Files          697      702       +5     
  Lines        54174    54208      +34     
===========================================
- Hits         42222    42193      -29     
- Misses       11952    12015      +63     

Flag	Coverage Δ
unittests	68.51% <19.04%> (-0.10%)	⬇️

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[stefanceriu]

Looks great 👍

[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