Replaces drcachesim's loops over all ways with a hashtable lookup. For larger cache hierarchies and caches with higher associativity this increases performance by 15% in cpu-bound tests on offline traces, when we use a large initial table size to avoid resizes which seem to outweigh the gains.
The hashtable unfortunately results in a 15% slowdown on simple cache hierarchies, due to the extra time in erase() and other maintenance operations outweighing the smaller gains in lookup. Thus, we make the default to not use a hashtable and use the original linear walk, providing a method to optionally enable the hashtable. The cache simulator enables the hashtables for any 3+-level cache hierarchy with either coherence or many cores.
Adds coherence to some existing 3-level-hierarchy tests to ensure we have tests that cover the hashtable path.
The TLB simulator will need to tweak these hashtables: but it looks like it is already doing the wrong thing in invalidate() and other simulator_t methods, filed as #4816.