feat: add witnesses for function_const_removed

[CommanderStorm]

Related to #937

A better whitness would be the following, but I have no clue if this is possible and if yes, how.
I have tried a few things, but I am missing something. Maybe this would require a query.

add() // if len(arguments) == 0
add(...) // if len(arguments) >= 1

=> is the compromise okay of letting this be add(...) to save on adding a whitness-query just for this?

[obi1kenobi]

Very nice, thank you!

For the witness hint, it's totally fine to omit the function arguments and just use .... We're just trying to give the user a broad-strokes idea of what might go wrong. Whether function args are present or not isn't that important in this situation so ... is fine.

Down the line, we'll have stricter rules for actual compilable witnesses as opposed to hints. But that's something for us to tackle down the line.