maple_tree: Drop bulk insert support

maple_tree: Drop bulk insert support

Bulk insert mode was added to facilitate forking faster, but forking now
uses __mt_dup() to duplicate the tree.

The addition of sheaves has made the bulk allocations difficult to
maintain - since the expected entries would preallocate into the maple
state.  A big part of the maple state node allocation was the ability to
push nodes back onto the state for later use, which was essential to the
bulk insert algorithm.

Remove mas_expected_entries() and mas_destroy_rebalance() functions as
well as the MA_STATE_BULK and MA_STATE_REBALANCE maple state flags since
there are no users anymore.  Drop the associated testing as well.

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