SF-3820 Fix race condition when viewing tabs that use the editor

[pmachapman]

This PR fixes a race condition that can cause the editor to not display under certain circumstances, particularly when viewing history.

I also took the opportunity to fix a bug I noticed while debugging this issue where a massive amount of CPU cycles were being consumed by formatDate when there were many items in the history dropdown. I fixed this by making the filter that contained the logic pure, but to ensure it updates when the locale changes, the locale is not passed to the filter.

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This change is 

[codecov]

Codecov Report

❌ Patch coverage is 87.50000% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 81.03%. Comparing base (0be7d55) to head (efff7c8).
✅ All tests successful. No failed tests found.

Files with missing lines	Patch %	Lines
.../editor/editor-history/editor-history.component.ts	66.66%	0 Missing and 1 partial ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #3981   +/-   ##
=======================================
  Coverage   81.03%   81.03%           
=======================================
  Files         645      645           
  Lines       41463    41464    +1     
  Branches     6750     6731   -19     
=======================================
+ Hits        33600    33601    +1     
- Misses       6755     6767   +12     
+ Partials     1108     1096   -12     

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