test: avoid flaky restart sync in debugger exceptions test

[inoway46]

Summary

This PR addresses the same flaky debugger restart race as #61773.

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/22050359911

• https://github.com/nodejs/node/actions/runs/22025863299
• https://github.com/nodejs/node/actions/runs/22532700362

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 89.64%. Comparing base (6a3d358) to head (bfe5f1b).
⚠️ Report is 2 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #62055      +/-   ##
==========================================
+ Coverage   89.58%   89.64%   +0.06%     
==========================================
  Files         674      676       +2     
  Lines      205159   206240    +1081     
  Branches    39352    39507     +155     
==========================================
+ Hits       183792   184891    +1099     
+ Misses      13583    13466     -117     
- Partials     7784     7883      +99     

see 124 files with indirect coverage changes

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