slice get_many_mut proof of concept

This is a POC to make [T]::get_many_mut to accept either an array of index or a tuple of index.

See the test folder for example of the API usage.

This POC introduces three new traits:

• SliceManyIndices<'slice, Slice: ?Sized> similar to SliceIndex<T> which is implemented for types that represent multiple indices (array and tuple) and gets the reference of the items from the slice.
• ManyIndices which is also implemented for types represents multiple indices. This trait provides runtime checking for "does the indices are distinct ?" and "does the indices in bounds ?".
• IndexOverlap<T> an operation that check if two index type overlap each other.

And one struct:

• DisjointIndices<I> which assert that the indices of a multiple indices value are disjoint.