- adding support for HTTP/3 test cases via a nghttpx server that is
build with ngtcp2 and nghttp3.
- test2500 is the first test case, performing a simple GET.
- nghttpx is checked for support and the 'feature' nghttpx-h3
is set accordingly. test2500 will only run, when supported.
- a specific nghttpx location can be given in the environment
variable NGHTTPX or via the configure option
--with-test-nghttpx=<path>
Extend NGHTTPX config to H2 tests as well
* use $ENV{NGHTTPX} and the configured default also in http2 server starts
* always provide the empty test/nghttpx.conf to nghttpx. as it defaults to
reading /etc/nghttpx/nghttpx.conf otherwise.
Added nghttpx to CI ngtcp2 jobs to run h3 tests.
Closes#9031
