ci: simplify tests

[wellwelwel]

Moving on #4091.

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Standardize every single test file to the describe + it or test pattern, for increased similarity to the widely adopted Node.js pattern.

All tests are now ES Modules, and for nested callbacks, new Promise is used instead of process.on(‘exit’, () => {}).

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Related

• Improve contributors and users experience #3695

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 89.95%. Comparing base (7726d27) to head (efed4cb).
⚠️ Report is 1 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #4092   +/-   ##
=======================================
  Coverage   89.95%   89.95%           
=======================================
  Files          86       86           
  Lines       13663    13663           
  Branches     1637     1636    -1     
=======================================
  Hits        12291    12291           
  Misses       1372     1372           

Flag	Coverage Δ
compression-0	89.07% <ø> (ø)
compression-1	89.93% <ø> (ø)
static-parser-0	87.54% <ø> (ø)
static-parser-1	88.30% <ø> (ø)
tls-0	89.36% <ø> (ø)
tls-1	89.73% <ø> (ø)

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