Fix creation of the NUMA node to heap number map

Fix creation of the NUMA node to heap number map

The current implementation assumes that the NUMA nodes of CPUs
used for GC threads form a zero based continous range. However that
doesn't have to be true for cases when user selects only a subset of the
available CPUs for the GC heap threads using the
COMPlus_GCHeapAffinitizeMask or COMPlus_GCHeapAffinitizeRanges. The
selected CPUs may belong only to a subset of NUMA nodes that don't
necessarily start at node 0 or form a continuous range.

This change fixes the algorithm that initializes the
numa_node_to_heap_map lookup array so that it works correctly even in
such cases.

Commit migrated from https://github.com/dotnet/coreclr/commit/9733c30b27ca90d3eeb07928df6e6e5861c203bb