Replace LTQ/CLQ with elimination stack

A lock-free Treiber stack backs off to the elimination array, which
borrows optimiztions from j.u.c.Exchanger. This is a work in progress,
with the stack needing to use Exchanger style spins. The time-to-idle
policy needs to be updates to be tolerant to running tasks out of
order.

An elimination stack avoids contention by allowing a thread performing
a push to cancel a concurrent thread performing a pop. This exchange
occurs in an elimination array when contention is observed on the
stack. When successful neither thread mutates the stack and higher
throughput is achieved.