chore: offload conversation calculation - WPB-17293

[dmitrysimkin]

Issue

Attempt to improve conversation screen performance issues
What was done:

• offload calculations of a sections to background thread. In order to do that I refetch messages in background thread, make calculations and re-set main thread selfUser and messages back to section controller
• Also made sectionControllers and actionControllers thread safe dictionary to synchronise access from 2 threads
• Added leading and trailing debounce for changes from DB, sometimes the are a lot of updates comes and we spam with them UI as well. Debounce limits amount of UI updates
• Removed nonPersistenceObjectIdentifier as It does not fit environment with 2 threads, it gives different IDs in different threads.

Testing

• All kind of message types
• See that all updates come and see in time (need to check because of usage of debounce)
• Long history with a lot of messages
• Live updates on hight load

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.

[samwyndham]

Apologies @dmitrysimkin for the slow review of this. Well done for fighting with this screen. To be honest this screen deserves a complete rewrite as I believe the current way it is implemented is fundamentally flawed.