Change IdxCache type to use Data.Parameterized.Map.

[brianhuffman]

This avoids a major performance regression with the hash table
implementation now used by parameterized-utils in module
Data.Parameterized.HashTable. (see GaloisInc/saw-script#674)

[brianhuffman]

The change appears to be just as fast on the s2n/BIKE proofs as it was when Data.Parameterized.HashTable used the cuckoo hash table implementation. I don't expect it will cause any big slow-downs, but out of an abundance of caution, we should check how this affects performance on other benchmarks besides s2n/BIKE before we think about merging it.

In the longer term, it might be nice if parameterized-utils provided a special-purpose map type for Nonce keys that was more efficient than an ordinary Map.

[robdockins]

Looks pretty straightforward to me. I'm OK if CI is green.

Slight longer term, we might want to make a specific NonceMap type in parameterized utils so we can slot in an IntMap style datastructure later.

[kquick]

I'll post s2n and bike results here when they are available from fryingpan.

[kquick]

This passes for all the important tests and the performance is much better than even the original cuckoo hashtable implementation. Looks good to merge!