feat(xray): add loopback sniffing and per-segment fragment masks

- Loopback outbound: add sniffing support (xray-core #6320)

- FinalMask fragment: support per-segment lengths/delays arrays with legacy length/delay migration (xray-core #6334)

- Consolidate sniffing into a shared SniffingFields component and the canonical SniffingSchema across inbound, VLESS reverse, and loopback

frontend/src/test/golden/fixtures/finalmask/tcp-fragment-segments.json

@@ -0,0 +1,13 @@
+{
+  "tcp": [
+    {
+      "type": "fragment",
+      "settings": {
+        "packets": "tlshello",
+        "lengths": ["10-20", "50-100"],
+        "delays": ["5-10", "0"],
+        "maxSplit": "0"
+      }
+    }
+  ]
+}