A lot of utility code was just being imported willy-nilly from one
package to another. This moves the common code into util to make things
more sensible. The code moved were
* The AsyncQueue and AsyncDecoupledCrossing from junctions.
* All of the code in rocket's util.scala
* The BlackBox asynchronous reset registers from uncore.tilelink2
* The implicit definitions from uncore.util
* [unittest] Parallelize UnitTestSuite so all tests have their own timer, runs until all finish or any timeout. Adds SimpleTimer.
* [util] Timer spacing cleanup
* [unittest] Remove Config reference to UnitTestTimeout