http,https: handle IPv6 with proxies

[joyeecheung]

This simplifies the proxy configuration handling code,
adds tests to make sure the proxy support works with IPv6
and throws correct errors for invalid proxy IPs.
Drive-by: remove useless properties from ProxyConfig

Refs: #57872

[nodejs-github-bot]

Review requested:

• @nodejs/crypto
• @nodejs/http
• @nodejs/net

[codecov]

Codecov Report

❌ Patch coverage is 92.00000% with 2 lines in your changes missing coverage. Please review.
✅ Project coverage is 88.29%. Comparing base (58f408f) to head (35d48f8).
⚠️ Report is 2 commits behind head on main.

Files with missing lines	Patch %	Lines
lib/https.js	85.71%	0 Missing and 1 partial ⚠️
lib/internal/http.js	94.44%	0 Missing and 1 partial ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##             main   #59894   +/-   ##
=======================================
  Coverage   88.29%   88.29%           
=======================================
  Files         702      702           
  Lines      206875   206883    +8     
  Branches    39797    39807   +10     
=======================================
+ Hits       182655   182671   +16     
+ Misses      16226    16212   -14     
- Partials     7994     8000    +6     

Files with missing lines	Coverage Δ
lib/https.js	98.23% <85.71%> (+0.15%)	⬆️
lib/internal/http.js	95.76% <94.44%> (+0.45%)	⬆️

... and 27 files with indirect coverage changes

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