test: allow half-open CONNECT tunnel sockets

[trivikr]

Refs: https://github.com/nodejs/reliability/issues?q=%22test-https-proxy-request-invalid-char-in-url%22

CONNECT tunnels are full-duplex. When the upstream socket receives a FIN while the client-to-upstream pipe is still draining, the default socket behavior can produce EPIPE or ECONNRESET errors.

Keep the upstream socket half-open so both directions can drain. Separate request logs from transport errors to verify that teardown completes without errors.

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Assisted-by: codex:gpt-5.6-sol

[trivikr]

Stress tests:

• main: https://ci.nodejs.org/job/node-stress-single-test/815/
• PR: https://ci.nodejs.org/job/node-stress-single-test/816/

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 90.27%. Comparing base (f43086d) to head (a83ef4f).
⚠️ Report is 2 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #64973      +/-   ##
==========================================
- Coverage   90.27%   90.27%   -0.01%     
==========================================
  Files         762      762              
  Lines      247515   247520       +5     
  Branches    46683    46680       -3     
==========================================
- Hits       223447   223445       -2     
- Misses      15485    15500      +15     
+ Partials     8583     8575       -8     

see 33 files with indirect coverage changes

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