dev: investigate Scarb macros to simulate a default entrypoint call

[enitrat]

CairoZero had __default__ entrypoints, calling default would fallback on a generic behavior. We don't have this now, but what we can do is create a special type of DefaultDispatcher, that would wrap the internal call to a call to __default__ on a given contract.

Perhaps this can be simplified with a Scarb Macro that, given a starknet interface, would generate the dispatcher that abstracts this default call.

[enitrat]

Tracking discussion starkware-libs/cairo#6170