test: split test-esm-wasm.js

[joyeecheung]

The test has been flaking due to either timeout or calling uv_async_send on a closing/closed handle. As the test squeezes too many independent test cases in one file, split it up to avoid timing out on slower machines and aid debugging.

Refs: https://github.com/nodejs/reliability/blob/main/reports/2025-10-29.md

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 88.57%. Comparing base (bfcf2f7) to head (9a5ee21).
⚠️ Report is 41 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #60491      +/-   ##
==========================================
- Coverage   88.58%   88.57%   -0.01%     
==========================================
  Files         704      704              
  Lines      207774   207828      +54     
  Branches    40026    40037      +11     
==========================================
+ Hits       184050   184088      +38     
- Misses      15759    15775      +16     
  Partials     7965     7965              

see 45 files with indirect coverage changes

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[lpinca]

RSLGTM