refactor: reduce usage of event.node.req

[pi0]

🔗 Linked issue

❓ Type of change

• 📖 Documentation (updates to the documentation, readme, or JSdoc annotations)
• 🐞 Bug fix (a non-breaking change that fixes an issue)
• 👌 Enhancement (improving an existing functionality like performance)
• ✨ New feature (a non-breaking change that adds functionality)
• 🧹 Chore (updates to the build process or auxiliary tools and libraries)
• ⚠️ Breaking change (fix or feature that would cause existing functionality to change)

📚 Description

This PR migrates most of internals to prefer top level or h3 utils instead of depending to event.node.req. (unjs/h3#73)

One major remaining part, is cachedEventHandler which currently uses a mock req, res. unjs/h3#472 might cover this!

Note: Deno is broken since installs h3 latest instead of rc (current dep)! Enabling tests after fixing it.

📝 Checklist

• I have linked an issue or discussion.
• I have updated the documentation accordingly.

[nuxt-studio]

✅ Live Preview ready!

Name	Edit	Preview	Latest Commit
nitro	Edit on Studio ↗︎	View Live Preview	41900a9

[codecov]

Codecov Report

Merging #1511 (535fe92) into main (f71cdeb) will decrease coverage by 0.06%.
The diff coverage is 25.00%.

❗ Current head 535fe92 differs from pull request most recent head 41900a9. Consider uploading reports for the commit 41900a9 to get more accurate results

@@            Coverage Diff             @@
##             main    #1511      +/-   ##
==========================================
- Coverage   76.22%   76.16%   -0.06%     
==========================================
  Files          73       73              
  Lines        7456     7456              
  Branches      732      731       -1     
==========================================
- Hits         5683     5679       -4     
- Misses       1772     1775       +3     
- Partials        1        2       +1     

Files Changed	Coverage Δ
src/dev/vfs.ts	9.44% <25.00%> (ø)

... and 1 file with indirect coverage changes