perf: use native fetch for node >= 18 to reduce %40 of bundle size

[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

Node.js 16 is EOL and by disabling the polyfill from node-fetch-native package, we can save almost %41 of the default bundle size!

This PR smartly enables experimental.nodeFetchCompact when Node.js 16 is being used with a warning to guide about an upgrade.

Output results

Node.js (current)
Σ Total size: 268 kB (69.9 kB gzip)

Node.js (native fetch)
Σ Total size: 158 kB (38.8 kB gzip)

We were also wrongly bundling polyfill for Bun which is not needed and it even saves more on bun (because of crypto export conditions mainly)

Bun (current)
Σ Total size: 255 kB (66.7 kB gzip)

Bun (native fetch)
Σ Total size: 146 kB (35.9 kB gzip)

📝 Checklist

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

[codecov]

Codecov Report

Merging #1724 (cc73b02) into main (08f0152) will increase coverage by 0.00%.
The diff coverage is 83.33%.

@@           Coverage Diff           @@
##             main    #1724   +/-   ##
=======================================
  Coverage   77.27%   77.27%           
=======================================
  Files          75       75           
  Lines        7893     7911   +18     
  Branches      806      806           
=======================================
+ Hits         6099     6113   +14     
- Misses       1792     1796    +4     
  Partials        2        2           

Files Changed	Coverage Δ
src/options.ts	96.30% <80.00%> (-0.70%)	⬇️
src/types/nitro.ts	100.00% <100.00%> (ø)