This change moves metadata structures that manage blocks of heap memory
out of the heaps in preparation for the W^X changes that will make the
heap memory read-execute only and modifying the metadata would require
unnecessary mappings and unmappings of the memory as read-write.

The structures moved in this change are the following:
* LoaderHeapBlock
* FreeBlock
* HeapList

* Replace malloc with new (nothrow) and add explicit contract violation
marker
* Remove unnecessary m_pCurBlock from the UnlockedLoaderHeap