tests(issue-views): Add tests and a couple of refactors

[MichaelSun48]

This PR adds the first round of tests for issue views, and it makes a couple of important refactors to the custom views component. Some of these are bug fixes that were uncovered by testing, others are other unrelated refactors. I will do my best to document these changes via comments.

I have also left some of the test sections blank with the intention of writing them up later in the interest of keeping this PR of reasonable length. There are significantly more tests to be written, and I think there are only benefits to writing them in stages.

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 79.16667% with 5 lines in your changes missing coverage. Please review.

:white_check_mark: All tests successful. No failed tests found.

Files with missing lines	Patch %	Lines
static/app/views/issueList/customViewsHeader.tsx	77.27%	5 Missing :warning:

Additional details and impacted files

@@            Coverage Diff             @@
##           master   #78539      +/-   ##
==========================================
+ Coverage   78.11%   78.19%   +0.08%     
==========================================
  Files        7082     7093      +11     
  Lines      312248   312442     +194     
  Branches    51010    51018       +8     
==========================================
+ Hits       243910   244317     +407     
+ Misses      61981    61782     -199     
+ Partials     6357     6343      -14     

[codecov[bot]]

Bundle Report

Changes will increase total bundle size by 114.99kB (0.37%) :arrow_up:. This is within the configured threshold :white_check_mark:

Detailed changes

Bundle name	Size	Change
app-webpack-bundle-array-push	30.97MB	114.99kB (0.37%) :arrow_up:

[getsentry-bot]

PR reverted: dfcdadb5df471ff281eb1377cc3e398c6f992af3