Profiling OCaml with perf

• perf support for DWARF vs FP vs LBR

• Importance of DWARF for performance tools like perf

Take content from ocaml/ocaml#12563, ocaml/ocaml#11144 and ocaml/ocaml#11031

LBR descriptions https://lwn.net/Articles/680985/ and https://lwn.net/Articles/680996/.