Create remove-track CLI command

[cmdcolin]

Fixes #1253

Also does some other small refactoring around the CLI tests

[codecov]

Codecov Report

Merging #3363 (42c4632) into main (4e69945) will increase coverage by 0.55%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##             main    #3363      +/-   ##
==========================================
+ Coverage   59.01%   59.56%   +0.55%     
==========================================
  Files         773      772       -1     
  Lines       29439    29414      -25     
  Branches     7116     7121       +5     
==========================================
+ Hits        17372    17520     +148     
+ Misses      11873    11700     -173     
  Partials      194      194              

Impacted Files	Coverage Δ
products/jbrowse-cli/src/base.ts	82.50% <100.00%> (ø)
products/jbrowse-cli/src/commands/remove-track.ts	100.00% <100.00%> (ø)
...ts/jbrowse-cli/src/commands/set-default-session.ts	96.49% <100.00%> (ø)
products/jbrowse-cli/src/testUtil.ts	93.65% <100.00%> (+1.98%)	⬆️
products/jbrowse-img/src/index.test.js
products/jbrowse-img/src/parseArgv.test.js
...aseLinearDisplay/models/BaseLinearDisplayModel.tsx	86.71% <0.00%> (+0.69%)	⬆️
...FeatureRenderer/components/SvgFeatureRendering.tsx	76.84% <0.00%> (+1.05%)	⬆️
plugins/alignments/src/BamAdapter/BamAdapter.ts	73.45% <0.00%> (+1.76%)	⬆️
...src/SvgFeatureRenderer/components/FeatureLabel.tsx	80.00% <0.00%> (+2.50%)	⬆️
... and 8 more

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[cmdcolin]

the whole thing about crashing session cause of a removed track is hard to advise users on properly but I figure this PR is otherwise good to go