TUN-3863: Consolidate header handling logic in the connection package; move headers definitions from h2mux to packages that manage them; cleanup header conversions

All header transformation code from h2mux has been consolidated in the connection package since it's used by both h2mux and http2 logic.
Exported headers used by proxying between edge and cloudflared so then can be shared by tunnel service on the edge.
Moved access-related headers to corresponding packages that have the code that sets/uses these headers.
Removed tunnel hostname tracking from h2mux since it wasn't used by anything. We will continue to set the tunnel hostname header from the edge for backward compatibilty, but it's no longer used by cloudflared.
Move bastion-related logic into carrier package, untangled dependencies between carrier, origin, and websocket packages.

carrier/carrier_test.go

@@ -156,3 +156,99 @@ func testRequest(t *testing.T, url string, stream io.ReadWriter) *http.Request {
 
 	return req
 }
+
+func TestBastionDestination(t *testing.T) {
+	tests := []struct {
+		name         string
+		header       http.Header
+		expectedDest string
+		wantErr      bool
+	}{
+		{
+			name: "hostname destination",
+			header: http.Header{
+				cfJumpDestinationHeader: []string{"localhost"},
+			},
+			expectedDest: "localhost",
+		},
+		{
+			name: "hostname destination with port",
+			header: http.Header{
+				cfJumpDestinationHeader: []string{"localhost:9000"},
+			},
+			expectedDest: "localhost:9000",
+		},
+		{
+			name: "hostname destination with scheme and port",
+			header: http.Header{
+				cfJumpDestinationHeader: []string{"ssh://localhost:9000"},
+			},
+			expectedDest: "localhost:9000",
+		},
+		{
+			name: "full hostname url",
+			header: http.Header{
+				cfJumpDestinationHeader: []string{"ssh://localhost:9000/metrics"},
+			},
+			expectedDest: "localhost:9000",
+		},
+		{
+			name: "hostname destination with port and path",
+			header: http.Header{
+				cfJumpDestinationHeader: []string{"localhost:9000/metrics"},
+			},
+			expectedDest: "localhost:9000",
+		},
+		{
+			name: "ip destination",
+			header: http.Header{
+				cfJumpDestinationHeader: []string{"127.0.0.1"},
+			},
+			expectedDest: "127.0.0.1",
+		},
+		{
+			name: "ip destination with port",
+			header: http.Header{
+				cfJumpDestinationHeader: []string{"127.0.0.1:9000"},
+			},
+			expectedDest: "127.0.0.1:9000",
+		},
+		{
+			name: "ip destination with port and path",
+			header: http.Header{
+				cfJumpDestinationHeader: []string{"127.0.0.1:9000/metrics"},
+			},
+			expectedDest: "127.0.0.1:9000",
+		},
+		{
+			name: "ip destination with schem and port",
+			header: http.Header{
+				cfJumpDestinationHeader: []string{"tcp://127.0.0.1:9000"},
+			},
+			expectedDest: "127.0.0.1:9000",
+		},
+		{
+			name: "full ip url",
+			header: http.Header{
+				cfJumpDestinationHeader: []string{"ssh://127.0.0.1:9000/metrics"},
+			},
+			expectedDest: "127.0.0.1:9000",
+		},
+		{
+			name:    "no destination",
+			wantErr: true,
+		},
+	}
+	for _, test := range tests {
+		r := &http.Request{
+			Header: test.header,
+		}
+		dest, err := ResolveBastionDest(r)
+		if test.wantErr {
+			assert.Error(t, err, "Test %s expects error", test.name)
+		} else {
+			assert.NoError(t, err, "Test %s expects no error, got error %v", test.name, err)
+			assert.Equal(t, test.expectedDest, dest, "Test %s expect dest %s, got %s", test.name, test.expectedDest, dest)
+		}
+	}
+}