Coq Platform & OCaml 5

[Blaisorblade]

At some point the platform should switch to OCaml 5. I'm opening this issue to track blockers, like CompCert. Cc @palmskog .

[palmskog]

As a memento, another current restriction with OCaml 5 and Coq is the lack of native_compute. The relevant Coq issues seem to be rocq-prover/rocq#10602 and rocq-prover/rocq#13940.