fix(rollup): use mlly as fallback resolver when externals disabled

[pi0]

🔗 Linked issue

resolves #947

❓ Type of change

• 📖 Documentation (updates to the documentation or readme)
• 🐞 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)
• ⚠️ Breaking change (fix or feature that would cause existing functionality to change)

📚 Description

When externals are disabled (workers like cf), we completely depend on rollup/node-resolve plugin which happens to fail resolving in pnpm monorepos. This PR adds mlly support as fallback which seems to supporting pnpm well and fixing resolving issue + a small fix for node+noExternals

📝 Checklist

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

[codecov]

Codecov Report

Merging #948 (36239a4) into main (db6e6c2) will decrease coverage by 0.17%.
The diff coverage is 26.08%.

@@            Coverage Diff             @@
##             main     #948      +/-   ##
==========================================
- Coverage   67.76%   67.59%   -0.17%     
==========================================
  Files          59       59              
  Lines        6009     6030      +21     
  Branches      676      679       +3     
==========================================
+ Hits         4072     4076       +4     
- Misses       1928     1945      +17     
  Partials        9        9              

Impacted Files	Coverage Δ
src/rollup/config.ts	88.30% <26.08%> (-3.37%)	⬇️

Help us with your feedback. Take ten seconds to tell us how you rate us. Have a feature suggestion? Share it here.

[timhanlon]

I ran into the pnpm monorepo vs Cloudflare Workers thing yesterday, thanks for this!