test_runner: refactor primordial-based Promise chains

[cjihrig]

This PR refactors two Promise chains in the test runner to use async/await style syntax instead. IMO this makes these two pieces of code significantly more readable (largely because of primordials), and will make some planned changes easier to implement.

test_runner: refactor build Promise in Suite()

This commit refactors the buildSuite Promise logic in the Suite
constructor to use an async function instead of creating an
awkward primordial-based Promise chain.

test_runner: refactor Promise chain in run()

This commit refactors the chain of functions in run() to use an
async function instead of creating an awkward primordial-based
Promise chain.

[nodejs-github-bot]

Review requested:

• @nodejs/test_runner

[aduh95]

Suggested change

	if (typeof postRun === 'function') {
	postRun();
	}
	if (typeof teardown === 'function') {
	teardown();
	}
	postRun?.();
	teardown?.();

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 87.98%. Comparing base (3178a76) to head (1b298a1).
Report is 2 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #55958      +/-   ##
==========================================
- Coverage   87.99%   87.98%   -0.01%     
==========================================
  Files         653      653              
  Lines      187852   187857       +5     
  Branches    35888    35885       -3     
==========================================
  Hits       165295   165295              
- Misses      15729    15734       +5     
  Partials     6828     6828              

Files with missing lines	Coverage Δ
lib/internal/test_runner/runner.js	89.10% <100.00%> (+0.17%)	⬆️
lib/internal/test_runner/test.js	96.95% <100.00%> (-0.02%)	⬇️

... and 24 files with indirect coverage changes

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[mcollina]

lgtm