Model Linux distro option in Conan recipes

CI needs to differentiate builds with different Linux distros also when using Conan.

We want to stick to upstream version of settings.yml so that users do not need to use
our version of it (a subsetting for Linux os for the distro) and merge it into their project(s).

This means that the only available way to model this is to have a "distro" Conan option declared in each module recipe. If used then it will affect the package-id and builds with different distros are treated as different binaries.

options = {"distro": ANY, .....}