Harmonize with roles

[cristovaoth]

This is WIP merge request. Some remarks:

• Bring in Structures Clearance and ExecutionOptions
  ** This triggered a rewrite of the main check function. The style used by this function is very similar to style used by the checkTransaction function in roles
• Adopt similar names for main functions:
  ** allowTarget
  ** revokeTarget
  ** scopeTarget
• Contrarily to roles, here ExecutionOptions are shared between Clearance.Target and Clearance.Function
  • For this reason, and even tho we could piggyback on allowTarget and scopeTarget to set options for free, I left the setExecutionOptions function as standalone. I think it could become ambiguous otherwise

Open question:

• There was a dedicated error string for when the fallback was targeted, and not allowed. The custom error was: "Fallback not allowed for this address"
• Under the current changes, such an error will be treat as any other not allowed function: "error FunctionNotAllowed()"
• Are we to keep the custom error?

[auryn-macmillan]

How to disambiguate between the fallback function and a function with the signature 0x00000000?

[cristovaoth]

I thought they were the same? I never thought about this, but this is true, technically there could be some signature out there that yields 0x00000000

I chatted about this Adam, and he agreed that in roles we would handle the fallback function case via this function signature, the bytes4(0)