[libc++][ranges] implement `std::views::elements_view`
`subrange` is also a `tuple-like`. To avoid the add entire `subrange` dependencies to `tuple-like`, we need forward declaration of `subrange`. However, the class template constraints of `subrange` currently requires `__iterator/concepts.h`, which requires `<concepts>`. The problem is that currently `tuple-like` is used in several different places, including libc++ extension for pair constructors. we don't want to add `<concepts>` to pair and other stuff. So this change also created several small headers that `subrange`'s declaration needed inside `__iterator/concepts/`
Differential Revision: https://reviews.llvm.org/D136268
NOKEYCHECK=True
GitOrigin-RevId: 94461822c75d5080bf648f86552f7a59b76905c9
diff --git a/docs/ReleaseNotes.rst b/docs/ReleaseNotes.rst
index 40c5951..6f08d95 100644
--- a/docs/ReleaseNotes.rst
+++ b/docs/ReleaseNotes.rst
@@ -66,6 +66,7 @@
- P0415R1 - ``constexpr`` for ``std::complex``
- P1208R6 - ``std::source_location``
- P0323R12 - ``std::expected``
+- P1035R7 - Input Range Adaptors
Improvements and New Features
-----------------------------