Tests/rewrite to snapshots

[zorkow]

Moves all tests that use our custom toXmlMatch method to use Jest's snapshot matching. The only exceptions are the tests in ConfigMacros. I need to think a bit about those.
Other tests that could probably be done with snapshot matching are those using toXmlArrayMatch.
Both are for a follow-up PR.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 86.49%. Comparing base (5caee44) to head (71f6868).

Additional details and impacted files

@@            Coverage Diff             @@
##           develop    #1442     +/-   ##
==========================================
  Coverage    86.49%   86.49%             
==========================================
  Files          340      340             
  Lines        86044    86044             
  Branches      4833     3190   -1643     
==========================================
  Hits         74425    74425             
- Misses       11595    11619     +24     
+ Partials        24        0     -24     

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[dpvc]

This looks great. Too bad we didn't know about this earlier!

Now that the tests are so much simpler to look at, the extra comment separators between tests probably aren't needed any more. Those were useful to help see where one test stopped and the next started when there were large MathML sections, but since those are no longer in the files, the separators are probably not needed. What do you think?