Fix issue 41413 (#41445)

Fix issue 41413 (#41445)

Fix the AV issue in GCHeap::ApproxTotalBytesInUse:

- The AV is fixed by stopping the iteration when seg1 becomes null
- don't count segments that have been decommited
- stop iterating when seg1 becomes freeable_soh_segment - this takes care of the case where we have put a segment on the list, but the OS call to decommit hasn't come back.

These fixes will still leave a window where the result will be inaccurate. To reduce the chances of an inaccurate result, we try this 3 times.