[libc++] Consistently replace `std::` qualification with `_VSTD::` or nothing. NFCI.

I used a lot of `git grep` to find places where `std::` was being used
outside of comments and assert-messages. There were three outcomes:

- Qualified function calls, e.g. `std::move` becomes `_VSTD::move`.
    This is the most common case.

- Typenames that don't need qualification, e.g. `std::allocator` becomes `allocator`.
    Leaving these as `_VSTD::allocator` would also be fine, but I decided
    that removing the qualification is more consistent with existing practice.

- Names that specifically need un-versioned `std::` qualification,
    or that I wasn't sure about. For example, I didn't touch any code in
    <atomic>, <math.h>, <new>, or any ext/ or experimental/ headers;
    and I didn't touch any instances of `std::type_info`.

In some deduction guides, we were accidentally using `class Alloc = typename std::allocator<T>`,
despite `std::allocator<T>`'s type-ness not being template-dependent.
Because `std::allocator` is a qualified name, this did parse as we intended;
but what we meant was simply `class Alloc = allocator<T>`.

Differential Revision: https://reviews.llvm.org/D92250

GitOrigin-RevId: d586f92c9456a972ee475a021525c0522b89587b
diff --git a/include/__tree b/include/__tree
index 404351b..26c4c41 100644
--- a/include/__tree
+++ b/include/__tree
@@ -967,7 +967,7 @@
 
 template<class _Tp, class _Compare>
 #ifndef _LIBCPP_CXX03_LANG
-    _LIBCPP_DIAGNOSE_WARNING(!std::__invokable<_Compare const&, _Tp const&, _Tp const&>::value,
+    _LIBCPP_DIAGNOSE_WARNING(!__invokable<_Compare const&, _Tp const&, _Tp const&>::value,
         "the specified comparator type does not provide a viable const call operator")
 #endif
 int __diagnose_non_const_comparator();
@@ -1120,7 +1120,7 @@
 
     _LIBCPP_INLINE_VISIBILITY
     size_type max_size() const _NOEXCEPT
-        {return std::min<size_type>(
+        {return _VSTD::min<size_type>(
                 __node_traits::max_size(__node_alloc()),
                 numeric_limits<difference_type >::max());}