Ensure correct behavior of Tuple methods that refer to the definition of Array methods

[nicolo-ribaudo]

Some of the tuple methods, such as Tuple.prototype.map, are defined with explicit steps and, when they have a callback, they pass the result of thisTupleValue(this) as the last parameter.
Other tuple methods, such as Tuple.prototype.forEach, are defined as a diff from the relative Array method, with references to this replaced with thisTupleVaue(this). However, array methods call ToObject(this) (which thus ends up being ToObject(thisTupleVaue(this)))) and pass the resulting object as the last parameter to the callback function.

In practice, this means that #[1].forEach((v, i, tup) => console.log(typeof tup)) logs "object" instead of "tuple": we should fix how we define those methods to make sure that the last parameter is correctly a primitive tuple.

Ref #317 (comment)

[ljharb]

I think the longer term approach is to actually have explicit spec steps instead of the indirect "x, but replace step y with z" approach.