[libc++][modularisation] Split <compare> into internal headers.

Differential Revision: https://reviews.llvm.org/D106107

NOKEYCHECK=True
GitOrigin-RevId: 61c35fb0c2c9e25942a913ea88f541dc5abb15e4
diff --git a/include/module.modulemap b/include/module.modulemap
index 2054186..cd77a4a 100644
--- a/include/module.modulemap
+++ b/include/module.modulemap
@@ -358,6 +358,11 @@
   module compare {
     header "compare"
     export *
+
+    module __compare {
+      module common_comparison_category { private header "__compare/common_comparison_category.h" }
+      module ordering                   { private header "__compare/ordering.h"                   }
+    }
   }
   module complex {
     header "complex"