Fix per object heap commit tracking for regions

[cshung]

We need to make sure the per object heap commit tracking feature works correctly under regions.

Right now, when a region are obtained from or returned to the regions free list, the committed_by_oh array is not updated. As a result, the memory is repurposed but the arrays are not updated, we need to fix that.

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Issue Details

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We need to make sure the per object heap commit tracking feature works correctly under regions.

Right now, when a region are obtained from or returned to the regions free list, the committed_by_oh array is not updated. As a result, the memory is repurposed but the arrays are not updated, we need to fix that.

Author:	cshung
Assignees:	cshung
Labels:	area-GC-coreclr
Milestone:	7.0.0