TUN-5600: Add coverage to component tests for various transports

This parameterizes relevant component tests by transport protocol
where applicable.
The motivation is to have coverage for (graceful or not) shutdown
that was broken in QUIC. That logic (as well as reconnect) is
different depending on the transport, so we should have it
parameterized. In fact, the test is failing for QUIC (and passing
for others) right now, which is expected until we roll out some
edge fixes for QUIC. So we could have caught this earlier on.

component-tests/constants.py

@@ -3,3 +3,7 @@ MAX_RETRIES = 5
 BACKOFF_SECS = 7
 
 PROXY_DNS_PORT = 9053
+
+
+def protocols():
+    return ["h2mux", "http2", "quic"]