feat(sub): map shadowsocks TCP HTTP headers to Mihomo's obfs plugin (#6838)

A shadowsocks inbound with a TCP HTTP header was dropped from Mihomo
subscriptions, although Mihomo's simple-obfs speaks the same wire format
(#6735). Such a node is now emitted with plugin: obfs, mode http and the request
Host header. Mihomo always requests GET /, and xray-core rejects a request whose
path is not one of the header's paths, so only headers that accept / map;
others stay dropped, as do non-shadowsocks protocols and the legacy Clash
endpoint.

internal/sub/clash_external_shadowsocks_test.go

@@ -30,7 +30,7 @@ func TestClashExternalShadowsocksMatchesInboundPath(t *testing.T) {
 			name:        "tcp http header",
 			stream:      `{"network":"tcp","security":"none","tcpSettings":{"header":{"type":"http","request":{"path":["/"],"headers":{"Host":["test"]}}}}}`,
 			link:        "ss://" + userinfo + "@203.0.113.1:8443?type=tcp&headerType=http&host=test#ss",
-			wantDropped: true,
+			wantDropped: false,
 		},
 		{
 			name:   "tls",