test: add a bunch of @inferred to the iterators test set (JuliaLang#56885)

The `@inferred` macro is applied to the following functions:
* `Base.IteratorSize`
* `Base.IteratorEltype`
* `eltype`
* `axes`
* `size`
* `length`
* `ndims`
* `isempty`

xref JuliaLang#56802

xref JuliaLang#56838

Author: nsajko