vquic: stabilization and improvements

vquic stabilization
- udp send code shared between ngtcp2 and quiche
- quiche handling of data and events improved

ngtcp2 and pytest improvements
- fixes handling of "drain" situations, discovered in scorecard
  tests with the Caddy server.
- improvements in handling transfers that have already  data or
  are already closed to make an early return on recv

pytest
- adding caddy tests when available

scorecard improvemnts.
- using correct caddy port
- allowing tests for only httpd or caddy

Closes #10451

tests/tests-httpd/test_05_errors.py

@@ -73,6 +73,8 @@ class TestErrors:
                               proto):
         if proto == 'h3' and not env.have_h3():
             pytest.skip("h3 not supported")
+        if proto == 'h3' and env.curl_uses_lib('quiche'):
+            pytest.skip("quiche not reliable, sometimes reports success")
         count = 5
         curl = CurlClient(env=env)
         urln = f'https://{env.authority_for(env.domain1, proto)}' \