Defined only if Allocator defines owns. Tries each allocator in
turn, in most-recently-used order. If the owner is found, it is moved to
the front of the list as a side effect under the assumption it will be used
soon.
Ternary.yes if one allocator was found to return Ternary.yes,
Ternary.no if all component allocators returned Ternary.no, and
Ternary.unknown if no allocator returned Ternary.yes and at least one
returned Ternary.unknown.
Defined only if Allocator defines owns. Tries each allocator in turn, in most-recently-used order. If the owner is found, it is moved to the front of the list as a side effect under the assumption it will be used soon.