usm: http2: tests: Add coverage for the bug

Added 2 tests, the first to check we are able to consume correctly frame that is split
to many packets.

The second to check an unsupported scenario (headers frame that its payload split on multiple packets)
does not prevent us from continue capturing valid requests on the connection

pkg/network/usm/usm_http2_monitor_test.go

@@ -1242,6 +1242,61 @@ func (s *usmHTTP2Suite) TestRawTraffic() {
 				}: 1,
 			},
 		},
+		{
+			name: "interesting frame split into multiple packets",
+			// Testing a scenario where an interesting frame is split into multiple packets.
+			// First, headers is split to frame-header and then frame-payload.
+			// Second, data is split to frame-header, portion of the frame-payload, and the rest of the frame-payload.
+			messageBuilder: func() [][]byte {
+				data := []byte("123456789")
+				headersFrame := newFramer().
+					writeHeaders(t, 1, usmhttp2.HeadersFrameOptions{Headers: generateTestHeaderFields(headersGenerationOptions{overrideContentLength: len(data)})})
+				headersLength := headersFrame.buf.Len()
+				frame := headersFrame.writeData(t, 1, true, data).bytes()
+				return [][]byte{
+					frame[:9],
+					frame[9:headersLength],
+					frame[headersLength : headersLength+9],
+					frame[headersLength+9 : headersLength+12],
+					frame[headersLength+12:],
+				}
+			},
+			expectedEndpoints: map[usmhttp.Key]int{
+				{
+					Path:   usmhttp.Path{Content: usmhttp.Interner.GetString(http2DefaultTestPath)},
+					Method: usmhttp.MethodPost,
+				}: 1,
+			},
+		},
+		{
+			name: "headers frame split into multiple packets unevenly",
+			// Testing a scenario where a headers frame is split into multiple packets in a way that the first packet
+			// contains the frame header and a couple of bytes from the frame payload, and the second packet contains
+			// the rest of the frame payload.
+			// This scenario is not supported, as we don't have the ability to reassemble the frame payload, and then
+			// to parse it.
+			// We check the unsupported scenario does not prevent us from capturing the next valid request.
+			messageBuilder: func() [][]byte {
+				data := []byte("123456789")
+				message := newFramer().
+					writeHeaders(t, 1, usmhttp2.HeadersFrameOptions{Headers: generateTestHeaderFields(headersGenerationOptions{overrideContentLength: len(data)})})
+				headersLength := message.buf.Len()
+				frame := message.writeData(t, 1, true, data).
+					writeHeaders(t, 3, usmhttp2.HeadersFrameOptions{Headers: headersWithGivenEndpoint("/bbb")}).
+					writeData(t, 3, true, emptyBody).bytes()
+				return [][]byte{
+					frame[:10],
+					frame[10:headersLength],
+					frame[headersLength:],
+				}
+			},
+			expectedEndpoints: map[usmhttp.Key]int{
+				{
+					Path:   usmhttp.Path{Content: usmhttp.Interner.GetString("/bbb")},
+					Method: usmhttp.MethodPost,
+				}: 1,
+			},
+		},
 	}
 	for _, tt := range tests {
 		t.Run(tt.name, func(t *testing.T) {