[FIRRTL] enable properties for inherent attributes

[youngar]

[FIRRTL] Clean up inferReturnTypes implementation
739cf51

This is a big change to clean up our implementation of
inferReturnTypes in an effort to get ourselves ready to enable
properties in the FIRRTL dialect. We had structured our API so that
inferReturnType would call out to a simpler version of itself with
some of the useless arguments removed. This prevented us from using op
adaptors to abstract over whether or not an inherent attribute was
contained inside the attr-dict or the properties.

This change keeps the old structure of a two level API, but with
different boundaries: The large API takes all arguments, creates an
adapter, pulls out the necessary attributes and then calls in to the
simpler interface. FIRParser uses the simpler API when inferring return
types. The simpler interface is now specific to each operation and not
common with other operations.

This last change caused a problem for parsePrimExp, which relied on a
generic interface to create all expressions. This function is now
templated over exactly how many arguments the specific prim op takes,
parses exactly that many, and splats them out when calling
inferReturnType. As an upside to this, we can also call a more
specific builder for each operation, which should speed up building
operations when we move to properties.

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[FIRRTL] enable properties for inherent attributes
f38c9b2
This enables properties in the FIRRTL dialect. Some op parsers which
called inferReturnTypes had to be updated to store inherent attributes
as properties on the OperationState, as the call to inferReturnTypes
expects properties to have already been populated. This is a change
that we should make for all operation parsers and builders, to make
things faster, but is not strictly necessary at this time.

[youngar]

On a firtool run, the change in performance is pretty close to a wash. Most passes got a little slower, some had bigger changes. This is newtime/oldtime again:
PrefixModules: %128
DropName: %36
Will do some profiling to see what is so slow.

[fabianschuiki]

Really cool to see this migrated over to properties. LGTM!

[youngar]

Thanks for taking a look!

[seldridge]

Impressive about DropNames. That has been such a trivial pass that has resisted speedups. A 2.7x speedup on that is awesome.