Add classic tests 3223-3226 and extend tests/http/test_12_reuse.py so that
connection reuse decisions are explicit:
- partial/aborted HTTP/1.1 responses must not reuse the connection
(premature multi_done closes non-multiplexed conns)
- different target hostnames must not share a connection even when they
resolve to the same address (url_match_destination)
- HTTP Basic credentials are per-request (PROTOPT_CREDSPERREQUEST), so
different -u values still reuse; assert that with num_connects
- same host positive control reuses (num_connects 1 then 0)
Closes#22224
