[libc++][CI] Switches to clang-format-16.

Uses an absolute path to the selected binary.
Updates the formatting of two files to match clang-format-16 style.

Depends on D144126

Reviewed By: #libc, philnik

Differential Revision: https://reviews.llvm.org/D144132
diff --git a/libcxx/src/memory_resource.cpp b/libcxx/src/memory_resource.cpp
index e00611dd..ca1d640 100644
--- a/libcxx/src/memory_resource.cpp
+++ b/libcxx/src/memory_resource.cpp
@@ -107,7 +107,7 @@
     new_res = new_res ? new_res : new_delete_resource();
     lock_guard<mutex> guard(res_lock);
     memory_resource* old_res = res;
-    res = new_res;
+    res                      = new_res;
     return old_res;
   } else {
     lock_guard<mutex> guard(res_lock);