implement `std::views::istream`

implement `std::ranges::basic_istream_view` and `std::views::istream`. Although the view itself is constexpr,
the constructor argument is a base class std::istream where its ctor/dtor are not constexpr. So no tests are performed in
constexpr

Differential Revision: https://reviews.llvm.org/D133317

NOKEYCHECK=True
GitOrigin-RevId: 96a509bca28b8668c3c2c68aae4116cc0d8c2952
diff --git a/include/module.modulemap.in b/include/module.modulemap.in
index dd7fd08..73e366f 100644
--- a/include/module.modulemap.in
+++ b/include/module.modulemap.in
@@ -1014,6 +1014,10 @@
       module enable_view            { private header "__ranges/enable_view.h" }
       module filter_view            { private header "__ranges/filter_view.h" }
       module iota_view              { private header "__ranges/iota_view.h" }
+      module istream_view           {
+        @requires_LIBCXX_ENABLE_LOCALIZATION@
+        private header "__ranges/istream_view.h"
+      }
       module join_view              { private header "__ranges/join_view.h" }
       module lazy_split_view        { private header "__ranges/lazy_split_view.h" }
       module non_propagating_cache  { private header "__ranges/non_propagating_cache.h" }