benchmark: throw on invalid type in fs and webstorage

[irontaek]

In 21 fs and webstorage benchmarks, the default: branch of the type switch
creates new Error('Invalid type') without throwing it. An unknown type then
falls through and benchmarks an undefined path instead of failing.

Before:

$ node benchmark/fs/bench-existsSync.js type=bogus n=10
fs/bench-existsSync.js n=10 type="bogus": 42,410.43975384981

After, the same command throws Error: Invalid type. Every type listed in each
benchmark's config still has a matching case, so valid runs are unchanged.

Disclosure: this change was found by a static check for discarded new Error(...)
expressions and prepared with a coding agent, which also ran the commands above.
I'll handle review feedback myself.

[nodejs-github-bot]

Review requested:

• @nodejs/performance

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[atlowChemi]

Probably worth adding a lint rule that doesn't allow calling the error constructor without throwing/assigning/returning it.
Maybe no-new could work, though might cause unrelated noise

[irontaek]

Good idea. no-new would flag ~310 sites (mostly tests that construct objects for side effects). A narrower selector next to the existing ThrowStatement one, ExpressionStatement > NewExpression[callee.name=/Error$/], flags only 2 sites after this PR — both intentional (benchmark/error/error.js measures Error construction, and test/parallel/test-errors-systemerror.js asserts the constructor throws), which I disabled inline. Added it as a second commit.

[irontaek]

Thanks, added the sign-off to both commits.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 90.48%. Comparing base (6c84c34) to head (2c08205).
⚠️ Report is 55 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff            @@
##             main   #66647    +/-   ##
========================================
  Coverage   90.47%   90.48%            
========================================
  Files         791      791            
  Lines      276800   277204   +404     
  Branches    53191    53306   +115     
========================================
+ Hits       250442   250825   +383     
- Misses      16778    16795    +17     
- Partials     9580     9584     +4     

see 55 files with indirect coverage changes

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