Fix CoreData concurrency

[olejnjak]

This PR fixes CoreData concurrency issues found by enabling -com.apple.CoreData.ConcurrencyDebug launch argument for demo app and for StreamChat test plans.

• I kept the launch argument for demo app and for both LLC test plans as I think it is useful to know about those issues
• fix issues in demo app
• fix issues in LLC tests

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Closes #954

[codecov]

Codecov Report

Merging #1026 (6669f34) into main (f23f8eb) will increase coverage by 0.02%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##             main    #1026      +/-   ##
==========================================
+ Coverage   89.97%   89.99%   +0.02%     
==========================================
  Files         213      214       +1     
  Lines        8986     9006      +20     
==========================================
+ Hits         8085     8105      +20     
  Misses        901      901              

Flag	Coverage Δ
llc-tests	89.82% <100.00%> (+0.02%)	⬆️
llc-tests-ios12	86.63% <100.00%> (+0.02%)	⬆️

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Impacted Files	Coverage Δ
...treamChat/Controllers/EntityDatabaseObserver.swift	100.00% <100.00%> (ø)
.../StreamChat/Controllers/ListDatabaseObserver.swift	93.45% <100.00%> (+0.28%)	⬆️
...ources/StreamChat/Database/DatabaseContainer.swift	97.03% <100.00%> (+0.13%)	⬆️
...at/Workers/Background/NewChannelQueryUpdater.swift	88.88% <100.00%> (+0.17%)	⬆️
...mChatTestTools/NSManagedObject+ContextChange.swift	100.00% <100.00%> (ø)

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[nuno-vieira]

LGTM! ✅ Thanks, didn't realise this flag wasn't ON already, it is very useful 👍

[VojtaStavik]

Looks great 👍 Just some minor changes and ergonomy tweaks.