Update OS and compilers in CI

[jcoupey]

We use Ubuntu for our CI builds and the next LTS is due by the end of the month so it's a good opportunity to upgrade:

• base image from ubuntu-22.04 to ubuntu-24.04;
• clang to version 18;
• gcc to version 13.

Potential blockers: 1. I have no idea when the new base will be available in GitHub actions and 2. it's fairly possible that building the upstream OSRM code will raise a handful of new problems with more recent compilers.

[jcoupey]

In order to unlock some pending PR/tickets, we need to move on with this.

First clear thing is that we'll never get to cleanly build OSRM v5.27.1 (current latest version) under Ubuntu 24.04 with more recent compilers. On the other hand, building OSRM with gcc 13 and clang 15 is now OK with master as of recent fixes.

Now the purpose of our vroom + libosrm workflow is to check whether we do not break anything related to using libosrm, or conversely checking that there is no upstream break with our current workflow. Considering that this has been useful in the past, and that our own libosrm integration code does not change much anyway, I think it makes sense that we upgrade OSRM to a latest version, even if it means pinning to a specific master commit until there is a new upstream release. I've started toying with this in #1113.