Merge pull request #2722 from ludovic-henry/fix-39279-docker-cpu-count

Merge pull request #2722 from ludovic-henry/fix-39279-docker-cpu-count

[utils] Get processor count from scheduler affinity if available

In case the user has set a scheduler CPU affinity, we should use it as the number of available CPU for the runtime. This is particularly important on docket which uses cgroups that set the container a cpu affinity, and by not using that, the runtime report the total number of CPU the machine has, and not the number of CPU the container has.

Fixes bug https://bugzilla.xamarin.com/show_bug.cgi?id=39279