jest-diff: Do not inverse format if line consists of one change

[pedrottimark]

Summary

It distracts attention of reviewer if entire change line has inverse format

Test plan

Updated snapshots:

	package	test
11	jest-diff	getAlignedDiffs
1	expect	matchers

Realistic regression tests for the win: the code change was more subtle than I thought

Example pictures baseline at left and improved at right

The inverse lines fight for attention with the substrings within lines:

The inverse lines add insult to injury when cleanup merges from and to into changes because common o is chaff:

To set the record straight, merging o chaff into from and to changes is good cleanup. The problem is the length criterion where common substring 'change '.length does not have greater length than adjacent change substring 'delete\n'.length so is merged into changes.

Notice the effect of one character increase in length to 'changed '

[codecov-io]

Codecov Report

Merging #8903 into master will increase coverage by <.01%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master    #8903      +/-   ##
==========================================
+ Coverage   64.24%   64.24%   +<.01%     
==========================================
  Files         275      275              
  Lines       11656    11658       +2     
  Branches     2844     2846       +2     
==========================================
+ Hits         7488     7490       +2     
  Misses       3544     3544              
  Partials      624      624

Impacted Files	Coverage Δ
packages/jest-diff/src/getAlignedDiffs.ts	100% <100%> (ø)	⬆️

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[SimenB]

Yeah, great call!

[github-actions]

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