test_runner: simplify logic, nix dead reporter code

[vassudanagunta]

While trying to understand the underlying logic of the built-in test reporters, necessary because documentation of the semantics of TestsStream is minimal, I was thoroughly confused by this code in formatTestReport:

const error = showErrorDetails ? formatError(data.details?.error, indent) : '';
const err = hasChildren ?
  (!error || data.details?.error?.failureType === 'subtestsFailed' ? '' : `\n${error}`) :
  error;

...and not just because of the obfuscation. It made sense that if data.details?.error?.failureType === 'subtestsFailed', the error should not be reported against the parent test, and even that this condition is only tested if hasChildren is true. But all callers that do pass in hasChildren (which otherwise defaults to false) also pass in  showErrorDetails: false, so that part of the convoluted nested ternary never even fires.

Ok, I thought, maybe formatTestReport represents an API the current built-in reporters do not use fully. But that seems a little odd because it is internal. So I reduced it to its essence, as currently used. I did it in four steps because I'm old and need to break things down more than you young'uns might need. Each step is a commit, with explanation in the commit message, with each commit passing all tests.

The upshot is the above gets reduced to

const err = showErrorDetails && data.details?.error ? 
  formatError(data.details.error, indent) : '';

along with an easier to understand formatTestReport function signature and removal of more dead code in the spec reporter.

[nodejs-github-bot]

Review requested:

• @nodejs/test_runner

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 89.92%. Comparing base (45a8b55) to head (44ccad8).
⚠️ Report is 7 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #59700      +/-   ##
==========================================
- Coverage   89.93%   89.92%   -0.02%     
==========================================
  Files         667      667              
  Lines      196792   196767      -25     
  Branches    38426    38405      -21     
==========================================
- Hits       176983   176939      -44     
- Misses      12233    12242       +9     
- Partials     7576     7586      +10     

Files with missing lines	Coverage Δ
lib/internal/test_runner/reporter/spec.js	96.49% <100.00%> (-0.15%)	⬇️
lib/internal/test_runner/reporter/utils.js	94.89% <100.00%> (+1.76%)	⬆️

... and 42 files with indirect coverage changes

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