To make it uniform in all tests, and greppability.
Also:
- replace `-k` flag with `-q` in test 1268. (the actual flag doesn't
matter in this test)
- keep `-k` in test 300 to test its short form.
(also verified to fail without a working `-k`)
Closes#16878
Check responsiveness of http/3 server when running.
Also, a test case with http/2 or http/3 server requirement
now implicitly drags in a 'http' server and we need no longer
mention that in testdata.
Closes#15058
Some feature names used in tests had minor differences compared to
the well-known ones from `curl -V`. This patch syncs them to make test
results easier to grok.
Closes#14183