feat: support transparent proxy accounts

[enitrat]

Related to #818, we want to replicate the behavior of accounts being transparent proxies and all calls being redirected to __default__.

[enitrat]

This will never be available natively in Cairo. What we could do is have a macro that generates a specific dispatcher calling and explicit default entrypoints, that itself makes a library call to the underlying class.

This way, we kind of achieve the transparent proxy behavior desired.