Implement pretty printing abstraction

[cptartur]

Right now, all printing within the forge source code is done just by calling methods from this module:

https://github.com/foundry-rs/starknet-foundry/blob/master/crates/forge/src/pretty_printing.rs

We should introduce a PrettyPrinting trait that will define necessary methods. Current code existing in pretty printing module should be used for creating a default implementation of that trait.

Code should be changed (e.g. here

starknet-foundry/crates/forge/src/lib.rs

Line 222 in 621a1a5

pretty_printing::print_collected_tests_count(

) so it depends on the new PrettyPrinting trait and the implementation should be injected into relevant functions.

[cptartur]

Related #74

[piotmag769]

Protostar Abstaction 💀

[MaksymilianDemitraszek]

Why do we need to introduce a new trait? Wouldn't be better to just use Display or sth?

[cptartur]

I don't think Display was designed to be used for that. We just want to decouple multiple possible output types of outputs from the runner code.