mm: Start tracking VMAs with maple tree

mm: Start tracking VMAs with maple tree

Start tracking the VMAs with the new maple tree structure in parallel
with the rb_tree.  Add debug and trace events for maple tree operations
and duplicate the rb_tree that is created on forks into the maple tree.

In this commit, the maple tree is added to the mm_struct including the
mm_init struct, added support in required mm/mmap functions, added
tracking in kernel/fork for process forking, and used to find the
unmapped_area and checked against what the rbtree finds.

Signed-off-by: Liam R. Howlett <Liam.Howlett@Oracle.com>