[libc++][ranges] implement `std::ranges::split_view`

- implement `std::ranges::split_view` (last c++20 view)
- Work in process on testing iterator/sentinel, but since we are
getting closer to the deadline, I'd like to send the review early

Differential Revision: https://reviews.llvm.org/D142063

NOKEYCHECK=True
GitOrigin-RevId: a2b3ab8f7786b9bb6e1b8bbb01b88d4bbe28af69
diff --git a/include/module.modulemap.in b/include/module.modulemap.in
index 5715775..1f1d67d 100644
--- a/include/module.modulemap.in
+++ b/include/module.modulemap.in
@@ -1256,6 +1256,7 @@
       module reverse_view           { private header "__ranges/reverse_view.h" }
       module single_view            { private header "__ranges/single_view.h" }
       module size                   { private header "__ranges/size.h" }
+      module split_view             { private header "__ranges/split_view.h" }
       module subrange               {
         private header "__ranges/subrange.h"