fix error message for eachindex(::Vararg{Tuple}) (#58811)

Make the error message in case of mismatch less confusing and consistent
with the error message for arrays.

While at it, also made other changes of the same line of source code:

* use function composition instead of an anonymous closure

* expand the one-liner into a multiline `if`

---------

Co-authored-by: Andy Dienes <51664769+adienes@users.noreply.github.com>

Author: nsajko

base/tuple.jl

@@ -150,7 +150,11 @@ nextind(@nospecialize(t::Tuple), i::Integer) = Int(i)+1
 function keys(t::Tuple, t2::Tuple...)
     @inline
     lent = length(t)
-    all(x->length(x) == lent, t2) || throw_eachindex_mismatch_indices(IndexLinear(), t, t2...)
+    if !all(==(lent) ∘ length, t2)
+        let inds = map(only ∘ axes, (t, t2...))
+            throw_eachindex_mismatch_indices("indices", inds...)
+        end
+    end
     Base.OneTo(lent)
 end