sysutils/turbostat: Fix reading topology with multiple packages

Fixed a bug where core identifiers within a package would not
count from zero. This caused a out-of-bounds array access when
multiple packages were present.

Also gracefully handle the absence of the kern.intrs sysctl (added
in 12.0), and don't use reallocarray (added in 11.0).

PR: 230066
Reported by: kbowling
Submitted by: D Scott Phillips <d.scott.phillips@intel.com> (maintainer)