Added Comments for CppInterOp's Doxygen based documentation

[QuillPusher]

I have added function definitions as Doxygen-style comments, based on the CppInterop information session between Baidyanath and Krishna.

Please review if my understanding was correct in these definitions (since I'm new to the domain).

Requested Reviewers: @vgvassilev @sudo-panda

[QuillPusher]

Squashed last 10 commits and summarized all comments into the last force-push commit, no new changes to the files