Show more descriptive errors from snforge plugin

[cptartur]

Currently, when args are incorrect, the error shown to the user doesn't indicate what the correct ones could be.

E.g.

error: Plugin diagnostic: #[should_panic] can be used with named attributes only
--> /Users/piotrmagiera/SWM/Dev/uwu/src/uwu.cairo[proc_test][proc___internal_config_statement]:2:1
#[should_panic("uwu")]
^********************^

Change the logic in snforge plugin to show more errors that clearly indicate what arguments are invalid and which options can be used instead.