layers : Update memory valid to be per-range

layers : Update memory valid to be per-range

We previously only tracked a single valid bool for an entire allocation.
That can easily get out of synch when multiple objects are bound to the
same allocation. This update moves the valid tracking to be per-range so
that it can be tracked on a per-object basis.

This does handle aliasing cases where various objects completely alias each
other, but there are still various aliased resource cases that aren't handled.