smart interactive tab completion

[whyvn]

• hinting & tab completion for commands
• hinting & tab completion for history
• smart hinting & tab completion based on argument type
• let State be accessed in Argument callbacks for some extra specifc hinting
• recurse for default subcommand hinting
• fix old commands to use new api (with proper hinting and everything)
  • load
  • run
  • step
  • reset
  • watchpoint
  • breakpoint
  • disassemble
  • context
  • label
  • labels
  • examine
  • print
  • dot
  • help
  • exit

plus some other stuff

• a variety of bug fixes
• Command now uses the builder pattern
• Argument has more stuff onw:

pub(crate) struct Argument {
    name: String,                                                                // argument name e.g. File, Step count, Whatever
    sanitiser: fn(arg: &str, helper: &MyHelper) -> CommandResult<ArgumentKind>,  // given some context, is this argument valid
    hints: fn(harg: &HintArgs, helper: &MyHelper) -> Vec<String>,                // what hints are available for this argument? (used for prompt hints and completion)
}

[whyvn]

hmm okay the next commit is going to restructure the arguments a bit. i think it should actually be a separate pr but im just doing it all at once here. i can revert and re pr later if i need to :)

[whyvn]

this feels very hacky. need to keep state here so we can give the Argument callbacks some program context to better hint and sanitise with.

maybe State and MyHelper should be combined? it didnt feel right to do that either though, so now theres just a reference but you have to pass a MyHelper ASWELL as a &mut State to every function that calls a command which feels veryveryvery clunky. im like 80% confident this should be changed

i was experimenting with a refcell or cow solution maybe it would be better

[whyvn]

im going to let MyHelper own State now. it could be a really bad idea but otherwise you have to clone the entire state every single tiime you run a command. untangling them should be easy if required though.

also having them together requires we pass a &mut MyHelper to exec callback which is a bit misleading since really we only want to be able to mutate the owned State