test: avoid flaky restart sync in debugger exceptions test

[inoway46]

Summary

In test/parallel/test-debugger-exceptions.js, using stepCommand('r') can intermittently time out while waiting for BREAK_MESSAGE.
For r, this PR switches restart sync to prompt-first waiting (command('r')) and then waits for waitForInitialBreak(), keeping test intent unchanged.

failed CI logs:

• https://github.com/nodejs/node/actions/runs/22025863299 (line:30)
• https://github.com/nodejs/node/actions/runs/22532700362 (line:41)
• https://github.com/nodejs/node/actions/runs/22632786580 (line:49)

Testing

UNUSUAL="$HOME/dir with \$unusual\"chars?'åß∂ƒ©∆¬…\`"
mkdir -p "$UNUSUAL"
ln -sfn "$PWD" "$UNUSUAL/node"
cd "$UNUSUAL/node"

• ./tools/test.py -p actions parallel/test-debugger-exceptions
• ./tools/test.py -p actions -j1 --repeat 40 parallel/test-debugger-exceptions
• ./tools/test.py -p actions parallel/test-debugger-restart-message parallel/test-debugger-run-after-quit-restart
• CI passes on macOS

Refs: #61762

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 89.70%. Comparing base (e78ccd8) to head (a3aa5ce).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main   #62055   +/-   ##
=======================================
  Coverage   89.70%   89.70%           
=======================================
  Files         691      691           
  Lines      213935   213935           
  Branches    41050    41040   -10     
=======================================
+ Hits       191907   191909    +2     
- Misses      14095    14109   +14     
+ Partials     7933     7917   -16     

see 38 files with indirect coverage changes

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[nodejs-github-bot]

CI: https://ci.nodejs.org/job/node-test-pull-request/71966/