fix: handle schema-less HTTP_PROXY env vars

[M-YasirGhaffar]

This relates to...

Fixes #4736

Rationale

When HTTP_PROXY or HTTPS_PROXY is set without a URL scheme (e.g., localhost:8080 instead of http://localhost:8080), the EnvHttpProxyAgent fails. This PR adds automatic http:// prefix for schema-less proxy URLs, matching Go's httpproxy behavior.

Changes

Added normalizeProxyUrl() helper function in lib/dispatcher/env-http-proxy-agent.js. Also added tests in test/env-http-proxy-agent.js.

Features

N/A

Bug Fixes

• Schema-less proxy URLs now work by assuming http:// protocol

Breaking Changes and Deprecations

None. This is additive behavior - existing URLs with explicit schemes are unchanged.

Status

• I have read and agreed to the Developer's Certificate of Origin
• Tested
• Benchmarked (optional)
• [S] Documented
• Review ready
• In review
• Merge ready

[mcollina]

cc @joyeecheung can you take a look as well?

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 93.26%. Comparing base (fc8bb75) to head (f052510).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #4809      +/-   ##
==========================================
- Coverage   93.26%   93.26%   -0.01%     
==========================================
  Files         109      109              
  Lines       34090    34098       +8     
==========================================
+ Hits        31794    31800       +6     
- Misses       2296     2298       +2     

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[metcoder95]

Will this require adjustments in Node for fetch besides the Undici upgrade?

[M-YasirGhaffar]

@metcoder95 This shouldn't require any changes for fetch. The normalization happens inside EnvHttpProxyAgent before the URL reaches ProxyAgent.