proxy: Identity integration tests don't exercise HTTP proxy #4947
Description
Tests like http[1|2]_outbound_tls_works_before_identity_is_certified don't actually exercise the http proxy. Instead, they incorrectly build their own TLS'd HTTP clients and servers, and then exercise the TCP proxy. In order to modify the TCP forwarding stack, these tests must be changed to exercise the actual proxy behavior.
If I understand correctly, all of the TLS-related infrastructure in the tests should be removed (client, server); and we should instead use normal plaintext clients and validate the states otherwise (headers? metrics?)
[ 0.33353667s] TRACE ThreadId(03) proxy{test=http1_outbound_tls_works_before_identity_is_certified:proxy}:outbound:accept{peer.addr=127.0.0.1:35580}: linkerd2_proxy_http::version: Not HTTP bytes=[22, 3, 1, 1, 17, 1, 0, 1, 13, 3, 3, 97, 162, 23, 33, 20, 185, 45, 122, 141, 51, 68, 175, 140, 253, 33, 2, 250, 197, 145, 41, 187, 74, 166, 191, 9, 123, 240, 107, 196, 86, 231, 188, 32, 171, 60, 74, 193, 51, 5, 120, 167, 88, 184, 141, 80, 92, 244, 225, 38, 205, 45, 214, 74, 220, 76, 53, 191, 143, 143, 11, 12, 175, 216, 195, 11, 0, 20, 19, 3, 19, 2, 19, 1, 204, 169, 204, 168, 192, 44, 192, 43, 192, 48, 192, 47, 0, 255, 1, 0, 0, 176, 0, 43, 0, 5, 4, 3, 4, 3, 3, 0, 0, 0, 58, 0, 56, 0, 0, 53, 98, 97, 114, 46, 110, 115, 49, 46, 115, 101, 114, 118, 105, 99, 101, 97, 99, 99, 111, 117, 110, 116, 46, 105, 100, 101, 110, 116, 105, 116, 121, 46, 108, 105, 110, 107, 101, 114, 100, 46, 99, 108, 117, 115, 116, 101, 114, 46, 108, 111, 99, 97, 108, 0, 11, 0, 2, 1, 0, 0, 10, 0, 8, 0, 6, 0, 29, 0, 24, 0, 23, 0, 13, 0, 18, 0, 16, 5, 3, 4, 3, 8, 6, 8, 5, 8, 4, 6, 1, 5, 1, 4, 1, 0, 23, 0, 0, 0, 5, 0, 5, 1, 0, 0, 0, 0, 0, 51, 0, 38, 0, 36, 0, 29, 0, 32, 208, 251, 16, 139, 56, 124, 247, 205, 106, 121, 70, 247, 210, 125, 134, 126, 228, 142, 160, 169, 204, 187, 150, 58, 167, 7, 48, 62, 173, 232, 51, 86, 0, 45, 0, 2, 1, 1, 0, 35, 0, 0]
[ 0.33470237s] TRACE ThreadId(03) proxy{test=http1_outbound_tls_works_before_identity_is_certified:proxy}:outbound:accept{peer.addr=127.0.0.1:35580}: linkerd2_proxy_http::version: h2.preface=[80, 82, 73, 32, 42, 32, 72, 84, 84, 80, 47, 50, 46, 48, 13, 10, 13, 10, 83, 77, 13, 10, 13, 10]
[ 0.33524683s] TRACE ThreadId(03) proxy{test=http1_outbound_tls_works_before_identity_is_certified:proxy}:outbound:accept{peer.addr=127.0.0.1:35580}: linkerd2_proxy_http::detect: Forwarding TCP