Instrument navToLocString tests in the LGV and fix refname navigation

[cmdcolin]

This tries to instrument some simple navToLocString tests for the LGV for easier testing of corner cases

There is likely more that can be done to ensure reliability but I hope these tests could be a starting point for simulating end-user behavior of using locstring inputs

Fixes #1740

[codecov]

Codecov Report

Merging #1741 (40b4b53) into master (d4bd417) will decrease coverage by 0.00%.
The diff coverage is 88.88%.

@@            Coverage Diff             @@
##           master    #1741      +/-   ##
==========================================
- Coverage   58.83%   58.83%   -0.01%     
==========================================
  Files         450      450              
  Lines       20845    20848       +3     
  Branches     4941     4942       +1     
==========================================
+ Hits        12265    12266       +1     
- Misses       8272     8274       +2     
  Partials      308      308              

Impacted Files	Coverage Δ
...s/linear-genome-view/src/LinearGenomeView/index.ts	84.04% <88.88%> (+0.26%)	⬆️
...inearGenomeView/components/RefNameAutocomplete.tsx	89.36% <0.00%> (-4.26%)	⬇️
packages/core/util/index.ts	82.20% <0.00%> (-0.33%)	⬇️

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