Rename interface for querying physical hardware concurrency

Based on post-commit review for D25585/r284180, rename
hardware_physical_concurrency to heavyweight_hardware_concurrency,
to better reflect what type of tasks it should be used for and
to enable other systems to map this to something other than the
number of physical cores.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@284390 91177308-0d34-0410-b5e6-96231b3b80d8
3 files changed