[hardikharti]

This PR adds SAI VXLAN decapsulation, 24-bit VNI-to-VRF tenant mapping, and end-to-end dataplane tests

Testing and validation summary:

Lemming Bazel Unit & End-to-End Tunnel Integration Tests
Branch: vxlan-decap

//dataplane/forwarding/protocol/packet:packet_test │ PASSED
//dataplane/forwarding/protocol/udp:udp_test │ PASSED
//dataplane/forwarding/protocol/vxlan:vxlan_test │ PASSED
//dataplane/saiserver:saiserver_test │ PASSED
//integration_tests/dataplane/tunnel:tunnel_test │ PASSED
//dataplane/forwarding/fwdport/ports:ports_test │ PASSED

//integration_tests/dataplane/tunnel:tunnel_test Subtest & Counter Summary :
=== RUN TestTunnelEncapDecap
--- PASS: TestTunnelEncapDecap (3.03s)
=== RUN TestVXLANTunnelEncapDecap
--- PASS: TestVXLANTunnelEncapDecap (10.27s)
PASS

port ate:port1,  tx enqueue 350, tx dequeue 350
port dut1:port1, rx enqueue 350, rx dequeue 350
port dut1:port2, tx enqueue 350, tx dequeue 350
port dut2:port1, rx enqueue 350, rx dequeue 350
port dut2:port2, tx enqueue 300, tx dequeue 300  (50 unmapped-VNI packets dropped)
port ate:port2,  rx enqueue 300, rx dequeue 300

Packet testing tool with SAI integration:

 Test Suite: SAI VXLAN Tunnel Test Suite
 Overall Status: PASSED
 Duration: 880.350732ms
======================================================
 [PASS] 1. VXLAN Decap and Forward to Overlay (24.75662ms)
 [PASS] 2. VXLAN Encap and Forward to Underlay (25.19237ms)
======================================================