fix(http1): accept unsolicited 100 responses

[GiHoon1123]

Fixes #5899

An unsolicited HTTP/1.1 100 Continue response should not terminate the connection. The client can ignore the interim response and continue parsing the final response.

The HTTP/1 parser was treating every 100 response as a bad response and destroying the socket. This change removes that special-case failure and keeps the existing informational-response handling.

The regression test covers:

• 100 Continue followed by a final 200 response
• response body delivery
• reuse of the same connection for a subsequent request

Tests:

• node --test test/http-100.js test/http2-informational.js
• npm exec -- eslint lib/dispatcher/client-h1.js test/http-100.js

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 91.54%. Comparing base (e960331) to head (8987ebb).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #5918   +/-   ##
=======================================
  Coverage   91.53%   91.54%           
=======================================
  Files         113      113           
  Lines       43597    43592    -5     
=======================================
- Hits        39908    39905    -3     
+ Misses       3689     3687    -2     

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[koal44]

I reported #5899. I tested this against my existing transport tests and added checks for repeated 100 responses, pipelined requests, and connection reuse. Everything checked out.

The Node 22 CI failure looks like the issue addressed by #5961, so it may be worth rebasing and rerunning CI.

[GiHoon1123]

Thanks for testing those cases. I rebased on the current main after #5961, and the new CI run passed, including the Node 22 job that failed before.