Add an OCaml 5 pipeline

[Sudha247]

Background

Add a new pipeline run for OCaml 5.0.0~alpha0.

Solution

Idea is to apply a git patch on top of tezos master branch (or other branches) to build it with OCaml 5.0. The branch is currently present here, https://github.com/ocaml-multicore/tezos/tree/trunk. I shall update here with a patch file for the same.

Outcome

OCaml 5 pipeline runs on Tezos CI for new PRs and the tezos master branch.

cc @moyodiallo @TheLortex