src: improve textEncoder encode performance with simdutf

[mertcanaltin]

ref: https://github.com/cloudflare/workerd/pull/5448/files

[codecov]

Codecov Report

❌ Patch coverage is 62.50000% with 21 lines in your changes missing coverage. Please review.
✅ Project coverage is 89.79%. Comparing base (ec56413) to head (0c17bf1).
⚠️ Report is 3 commits behind head on main.

Files with missing lines	Patch %	Lines
src/encoding_binding.cc	62.50%	16 Missing and 5 partials ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #61496      +/-   ##
==========================================
- Coverage   89.80%   89.79%   -0.01%     
==========================================
  Files         672      672              
  Lines      203907   203955      +48     
  Branches    39202    39201       -1     
==========================================
+ Hits       183114   183138      +24     
- Misses      13115    13140      +25     
+ Partials     7678     7677       -1     

Files with missing lines	Coverage Δ
src/encoding_binding.cc	52.96% <62.50%> (+0.22%)	⬆️

... and 27 files with indirect coverage changes

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.
• 📦 JS Bundle Analysis: Save yourself from yourself by tracking and limiting bundle sizes in JS merges.