retsnoop: support capturing and pretty-printing function input arguments

[anakryiko]

We can rely on BTF and libbpf APIs (e.g., btf_dump__dump_type_data()) to capture and emit input arguments.

Again, major considerations are usability: how to let user to specify when and what to capture and output, and how large structs should be formatted in the output.

[anakryiko]

Done in https://github.com/anakryiko/retsnoop/pull/63 and subsequent changes.