[fpmsyncd]: Add support for SRv6 (sonic-net#3123)

* [fpmsyncd]: Add support for SRv6
What I did
Extended fpmsyncd to process Netlink TLVs containing SRv6 information (SRv6 local SIDs and routes).
Extend fpmsyncd to process SRv6 routes and local SIDs received from FRR
Add test cases to verify SRv6 functionality

Why I did it
fpmsyncd did not process Netlink TLVs containing SRv6 information (SRv6 local SIDs and routes).

Author: cscarpitta

fpmsyncd/fpmlink.cpp

@@ -43,6 +43,11 @@ bool FpmLink::isRawProcessing(struct nlmsghdr *h)
 
     rtm = (struct rtmsg *)NLMSG_DATA(h);
 
+    if (h->nlmsg_type == RTM_NEWSRV6LOCALSID || h->nlmsg_type == RTM_DELSRV6LOCALSID)
+    {
+        return true;
+    }
+
     if (h->nlmsg_type != RTM_NEWROUTE && h->nlmsg_type != RTM_DELROUTE)
     {
         return false;

fpmsyncd/fpmlink.h

@@ -15,6 +15,9 @@
 #include "fpmsyncd/fpminterface.h"
 #include "fpmsyncd/routesync.h"
 
+#define RTM_NEWSRV6LOCALSID		1000
+#define RTM_DELSRV6LOCALSID		1001
+
 namespace swss {
 
 class FpmLink : public FpmInterface {