test: avoid orphaned child on Windows abort test

[PickBas]

Problem

On Windows, test-child-process-exec-abortcontroller-promisified can leave stray node.exe processes behind after the test exits.

exec() runs the command through cmd.exe, and cmd.exe cannot replace itself with the command it runs, so the node.exe started for -e "setInterval(()=>{}, 99)" is a grandchild. child.kill() terminates only the direct child, leaving that grandchild orphaned if the kill lands after cmd.exe has already created it. This is timing-dependent and does not reproduce on every machine.

Fix

Use the cmd.exe builtin pause as the wait command. It blocks on the stdin pipe that exec() opens and spawns no process of its own, so cmd.exe is the only process in the tree and killing it leaves nothing behind.

Fixes: #58118

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 90.14%. Comparing base (fd5b135) to head (8ce0003).
⚠️ Report is 24 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #65451      +/-   ##
==========================================
+ Coverage   90.12%   90.14%   +0.01%     
==========================================
  Files         752      752              
  Lines      252325   252315      -10     
  Branches    47456    47454       -2     
==========================================
+ Hits       227407   227437      +30     
+ Misses      16217    16181      -36     
+ Partials     8701     8697       -4     

see 58 files with indirect coverage changes

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