Add a member validating fixed size inhomogeneous tuple

[MatthieuDartiailh]

Currently the Tuple member can only validate tuple which are homogeneous in type and we do not validate the length. This is at odd with typing.Tuple which can be used for fixed sized tuple and in-homogeneous types. We could add a member mimicking typing.Tuple.

Is such a feature of interest to others ?

[MatthieuDartiailh]

I am also interested in bikeshedding the name of this member (we cannot just use Tuple for backward compatibility reasons):

• SizedTuple
• FixedTuple
• ...

[MatthieuDartiailh]

Closed by #211