Record number of physical cores on all platforms

The db.hostInfo() helper already records the number of logical cores for most customer systems and even limits to what's actually available inside a container with cgroups (see SERVER-40506) but doesn't capture physical cores except on MacOS.

In terms of auditing host capacities across larger MongoDB deployments, it would be useful to also capture physical core counts and expose this value via db.hostInfo()'s existing hostInfo.extra.physicalCores field .