fix: preserve connect option in H2CClient

[trivikr]

This relates to...

Fixes: #4999

Rationale

H2CClient destructured connect out of clientOpts and then never forwarded it to Client. That caused custom connectors to be silently ignored, and invalid connect values were no longer rejected through Client's existing validation path.

Changes

Forward connect implicitly by leaving it inside ...opts when constructing Client.

Add a regression test covering custom connect usage in H2CClient.

Features

N/A

Bug Fixes

Restore support for the connect option in H2CClient.

Breaking Changes and Deprecations

N/A

Status

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

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 92.92%. Comparing base (743aa89) to head (a4ed737).

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #5000   +/-   ##
=======================================
  Coverage   92.92%   92.92%           
=======================================
  Files         110      110           
  Lines       35729    35729           
=======================================
  Hits        33201    33201           
  Misses       2528     2528           

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[mcollina]

lgtm