net: ignore UV_EALREADY in tryReadStart

[harjothkhara]

tryReadStart() treated every non-zero readStart() result as fatal. That
included UV_EALREADY, which means the handle is already reading and no
additional action is required.

Ignore UV_EALREADY while preserving the existing socket destruction path for
all other read-start errors. Add a loopback regression test that forces this
return value and verifies that the socket remains usable.

Fixes: #62400

Tests:

• make -j8
• tools/test.py test/parallel/test-net-read-start-ealready.js
• tools/test.py test/parallel/test-net-*.js
• make lint-js

AI assistance: OpenAI Codex assisted with implementation and validation. Local
Claude and Codex review passes reported no actionable findings.

[nodejs-github-bot]

Review requested:

• @nodejs/net

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 90.23%. Comparing base (608112a) to head (51e7fce).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #64530      +/-   ##
==========================================
+ Coverage   90.21%   90.23%   +0.01%     
==========================================
  Files         739      739              
  Lines      241650   241651       +1     
  Branches    45542    45553      +11     
==========================================
+ Hits       218013   218054      +41     
+ Misses      15155    15110      -45     
- Partials     8482     8487       +5     

Files with missing lines	Coverage Δ
lib/net.js	94.37% <100.00%> (+<0.01%)	⬆️

... and 24 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.