Add comprehensive security tests for masking and shape hardening features

- Introduced red-team expected-fail tests for client masking shape hardening.
- Added integration tests for masking AB envelope blur to improve obfuscation.
- Implemented masking security tests to validate the behavior of masking under various conditions.
- Created tests for masking shape above-cap blur to ensure proper functionality.
- Developed adversarial tests for masking shape hardening to evaluate robustness against attacks.
- Added timing normalization security tests to assess the effectiveness of timing obfuscation.
- Implemented red-team expected-fail tests for timing side-channel vulnerabilities.

src/proxy/tests/masking_security_tests.rs

@@ -1321,6 +1321,8 @@ async fn relay_to_mask_keeps_backend_to_client_flow_when_client_to_backend_stall
             false,
             0,
             0,
+            false,
+            0,
         )
         .await;
     });
@@ -1424,7 +1426,18 @@ async fn relay_to_mask_timeout_cancels_and_drops_all_io_endpoints() {
 
     let timed = timeout(
         Duration::from_millis(40),
-        relay_to_mask(reader, writer, mask_read, mask_write, b"", false, 0, 0),
+        relay_to_mask(
+            reader,
+            writer,
+            mask_read,
+            mask_write,
+            b"",
+            false,
+            0,
+            0,
+            false,
+            0,
+        ),
     )
     .await;