Fix: Increase keepalive and HTTP request timeouts to prevent CI failures

[julianz-]

These fixes address:

1. The test_keepalive_conn_management test was intermittently failing in CI with http.client.NotConnected. This was due to the combined execution time of test logic and the explicit time.sleep() exceeding the server timeout (2.0s).

2. The http_request_timeout was also too short and causing failures in test_http_over_https_error().

This commit addresses the flakiness by increasing both timeout values.

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This change is 

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 79.31%. Comparing base (4f040de) to head (8dea118).
⚠️ Report is 160 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #777   +/-   ##
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  Coverage   79.31%   79.31%           
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  Files          29       29           
  Lines        4197     4197           
  Branches      538      538           
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  Hits         3329     3329           
  Misses        726      726           
  Partials      142      142           

[webknjaz]

@julianz- could you also link the example failures you were seeing in actual CI logs?

[julianz-]

@julianz- could you also link the example failures you were seeing in actual CI logs?

Here's a link for the failure with test_keepalive_conn_management().
https://github.com/cherrypy/cheroot/actions/runs/18145322195/job/51645700584?pr=764 for test_keepalive_conn_management() failure

Unfortunately, I can't find a log for the other timeout failure now. I saw it many times but it's bit of a nightmare rummaging through all these builds. I can drop this change and see it if comes back again.

[webknjaz]

Alright, I've skimmed through the second test and even though there's no log to check, the timeout change doesn't seem harmful so I'll just go with it. Thanks!