[xla:runtime] Add BufferUse to track buffer slice read/write conflicts
[xla:runtime] Add BufferUse to track buffer slice read/write conflicts

This already exists in gpu backends here: https://github.com/openxla/xla/blob/e308cd376175de82627d29a959cea5cf458b5ea4/xla/service/gpu/runtime/command_buffer_cmd.h#L80-L97. Moving to shared component in preparation for runtime unification.
