[libc++] Rename __libcpp_assertion_handler to __libcpp_verbose_abort

With the goal of reusing that handler to do other things besides
handling assertions (such as terminating when an exception is thrown
under -fno-exceptions), the name `__libcpp_assertion_handler` doesn't
really make sense anymore.

Furthermore, I didn't want to use the name `__libcpp_abort_handler`,
since that would give the impression that the handler is called
whenever `std::abort()` is called, which is not the case at all.

Differential Revision: https://reviews.llvm.org/D130562

NOKEYCHECK=True
GitOrigin-RevId: 507125af3d0b953cb56bce2e5b8000249fe1ef53
diff --git a/include/module.modulemap.in b/include/module.modulemap.in
index 88f4d15..8777db3 100644
--- a/include/module.modulemap.in
+++ b/include/module.modulemap.in
@@ -1294,6 +1294,7 @@
   module __tree              {         header "__tree"              export * }
   module __tuple             { private header "__tuple"             export * }
   module __undef_macros      {         header "__undef_macros"      export * }
+  module __verbose_abort     {         header "__verbose_abort"     export * }
 
   module experimental {
     requires cplusplus11