[libc++][ranges] LWG3984: ranges::to's recursion branch may be ill-formed (#87964)

This pull request implements LWG3984: ranges::to's recursion branch
may be ill-formed.

In the current implementation, ranges::to's recursion branch pipes the
range into a `views::transform(/* lambda */)`, which is a __range_adaptor_closure
object. In libc++, the pipe operator of __range_adaptor_closure requires a
viewable_range, so the following code won't compile, as the type of lvalue
`r` doesn't model viewable_range:

  #include <ranges>
  #include <vector>
  #include <list>

  int main() {
    std::vector<std::vector<int>> v;
    auto r = std::views::all(std::move(v));
    auto l = std::ranges::to<std::list<std::list<int>>>(r);
  }

Co-authored-by: A. Jiang <de34@live.cn>