Update benchmarks and domainslib to support ocaml 4.14.0+domains (ocaml 5.0)

[shubhamkumar13]

This PR is the first step in adding ocaml 5.0 support for the benchmarks in sandmark.

The PR adds domainslib.0.3.2 and updates the benchmarks supporting the updated api for domainslib

[shakthimaan]

# OCaml version mismatch: 5.00.0, expected 4.14.0

The version number mismatch is causing the 4.14.0+trunk build to fail. The following issue is related: ocaml-multicore/ocaml-multicore#709.

[kayceesrk]

Looks like upstream has changed the version number to 5.00.0: https://github.com/ocaml/ocaml/blob/trunk/VERSION#L1. So 4.14.0+trunk should be 5.00.0+trunk.

[kayceesrk]

Ping @shubhamkumar13.

[shubhamkumar13]

I've added an issue tracing irmin benchmarks failing on ocaml.5.00.0+trunk which would be fixed when the trunk is frozen (which would be easier for generating ppxlib version supporting trunk).

I think it's best to merge this before and then #257 can be merged (since there are changes to drome.yml file where I've updated the trunk from 4.14.0+trunk to 5.00.0+trunk)

[shubhamkumar13]

This PR also updates drone.yml file to 5.00.
This is in addition to the adding the updated domainslib and making benchmarks compatible to 5.00