Write unified routines for route installation in Ribs

[sachinites]

Currently, we install separate routines for installing native IGP routes and SR routes in respective ribs. We need to write common routine to achieve the same goal. Reason for this is that, for features which require to implement the logic in route installation path would need to be implemented twice (code duplicacy) in both routines.
If we have one unified routine, then future features (such as microloop avoidance) can be easily implemented. Only implementation would work for all types of routes (IGP or SR).

[sachinites]

Another problem is that : Currently, we install primary nexthops and backup nexthops one by one in RIB for each route. We need to push the entire route along with all nexthops (primary and backups) into RIB in one go.