IS-IS update 4: optimizing agent framework

Updated the #agent #framework in IS-IS module. The #generic #IS-IS #framework has been #optimized to use shorter #variable #names and removed the #length variable for many #multi-size #parameters. This makes uses of short & easier variable names. The memory size of many multi-size variables have been made static and length support has been removed reducing the memory requirement.

#IS-IS update 4 ...
[commit 253a05a0c60371b2864f3d631461404b5e347d7e] (https://github.com/nes-repo/NES-Open-Switch/commit/253a05a0c60371b2864f3d631461404b5e347d7e)