Externalize creation of Chat collection view layout models

[jrcmramos-bumble]

This PR decouples the adapter from the creation of collection items diff.
Since this operation can take some time, this could block the release of ChatMessageCollectionAdapter, since it was retaining it.

[gsherofly007]

您好，邮件收到

[codecov-commenter]

Codecov Report

Merging #741 (58fba30) into master (1f4f9a7) will increase coverage by 0.01%.
The diff coverage is 100.00%.

❗ Current head 58fba30 differs from pull request most recent head 70cb421. Consider uploading reports for the commit 70cb421 to get more accurate results

@@            Coverage Diff             @@
##           master     #741      +/-   ##
==========================================
+ Coverage   54.84%   54.86%   +0.01%     
==========================================
  Files         108      110       +2     
  Lines        5745     5760      +15     
==========================================
+ Hits         3151     3160       +9     
- Misses       2594     2600       +6     

Impacted Files	Coverage Δ
...oller/ChatMessages/ChatCollectionItemsDiffer.swift	100.00% <100.00%> (ø)
...essages/ChatCollectionViewLayoutModelFactory.swift	100.00% <100.00%> (ø)
...er/ChatMessages/ChatMessageCollectionAdapter.swift	78.12% <100.00%> (-2.96%)	⬇️
...Chat Items/TextMessages/Views/TextBubbleView.swift	82.44% <0.00%> (-3.20%)	⬇️

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