Better struct handling in code generation util

[webthethird]

Generates better code, which will compile without manual editing, when dealing with structs.

• Avoids using a struct's canonical name, which will not match the generated interface once an I is prepended to the contract name
• Handles arrays of structs in function parameters and returns
• Handles nested mappings inside and outside of structs
• Handles structs defined in other contracts/libraries
• Converts the type of enums used in structs, in case include_enums is false

Resolves this issue in crytic/diffusc, where the generated interface would not compile due to a reference in a function signature to a struct defined in another contract.

Replaces #1933

[0xalpharush]

Can you add the failing example as a regression test and run make reformat please?

[webthethird]

Can you add the failing example as a regression test and run make reformat please?

Done!