[Core] Rename ptr src and dst to client and server

[vaastav]

In GitLab by @JonathanMace on Sep 19, 2023, 20:29

Currently, pointers use src and dst to refer to the caller and callee side of things respectively. Rename this to client and server. Although client and server is actually more specific than what pointers can represent, the terminology is more clear than src and dst.