feat(PXE): Querying contract public information form an app

[spalladino]

While we have a decodeReturnValues helper that can be used for converting the return values of a view call, this requires an ABI definition, which we don't have when reading directly from storage via a getPublicStorageAt call.

We should expose helper functions that make it easy to go from a flattened array of fields to a type defined by the user without having an ABI definition for it. Perhaphs it's as simple as requiring only an ABIType instead of a FunctionArtifact as input to decodeReturnValues..?

Requested by Wonderland

[rahul-kothari]

so perhaps storage and user defined structs in the ABI? is there any downside to that?

[rahul-kothari]

@spalladino would it be fair for me to re-title this issue to "make storage declarative in the ABI"?

[spalladino]

@rahul-kothari I think making storage declarative is half of it. The other half is having a nice API (in aztecjs?) that uses the raw getStorageAts exposed by the node/pxe, and then uses the declarative storage info to properly decode it.

[LHerskind]

This issue seems very related to #2806 and both benefit from #5079.