Fix a bug where a new line in the composer could move the caret.

[pixlwave]

Fixes #3104.

The diffs revealed some missing attributes on the new line so I'm only restoring the selection when the plain string is unchanged.

[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 756d25d

[sonarcloud]

Quality Gate passed

Issues
0 New issues
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 50.00000% with 4 lines in your changes missing coverage. Please review.

Project coverage is 77.57%. Comparing base (cdaa88e) to head (756d25d).
Report is 1 commits behind head on develop.

Files	Patch %	Lines
...omposerToolbar/View/MessageComposerTextField.swift	50.00%	4 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff             @@
##           develop    #3114      +/-   ##
===========================================
- Coverage    77.80%   77.57%   -0.24%     
===========================================
  Files          713      714       +1     
  Lines        54994    55386     +392     
===========================================
+ Hits         42786    42963     +177     
- Misses       12208    12423     +215     

Flag	Coverage Δ
unittests	68.32% <50.00%> (+0.01%)	⬆️

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