Upgrade to Conan 2

[kyllingstad]

This is just #55 again. I reverted that pull request because it depends on open-simulation-platform/libcosim#753, which is not in a release yet. (More details in this comment.)

We have to choose between these two options:

1. Make a new libcosim release before merging this, so libcosimc master can continue to use the libcosim@osp/stable package.
2. Switch to using libcosim@osp/testing (which tracks libcosim master) in libcosimc master.

[kyllingstad]

Aw man, master is still broken despite the fact that I reverted all my changes to it. The problem is that our dependencies have moved on and no longer support the Conan version we use in our CI setup. That makes it all the more urgent to resolve the questions above and get this merged (again).