Added multiplication and division operators for Bytes.

Review: https://reviews.apache.org/r/28983
Split apart the Bytes test.

Review: https://reviews.apache.org/r/28984
Updated Resources interface to expose reservations.

Review: https://reviews.apache.org/r/28985
Removed Resources::extract in favor of reservation-based helpers.

Review: https://reviews.apache.org/r/28986
Added an allocator unit test for allocatable resources.

Review: https://reviews.apache.org/r/28987
Fixed the two level sorting in the allocator.

Review: https://reviews.apache.org/r/28824