[compiler-rt] Simplify and rename of operator_new_size_type

We can rely on the compiler-provided macro __SIZE_TYPE__ for all
non-MSVC compilers and fall back to `uptr` otherwise.
I verified via https://godbolt.org/z/MW9KMjv5f that this works for MSVC
as well as GCC 4.5 Clang 3.0, so that should cover supported compilers.

While touching this also rename operator_new_size_type to usize which
makes it more obvious that this is the equivalent to size_t within
the sanitizers runtime (which I plan to use in follow-up changes).

Reviewed By: vitalybuka

Pull Request: #83912

compiler-rt/lib/sanitizer_common/sanitizer_common.h

@@ -1098,7 +1098,7 @@ inline u32 GetNumberOfCPUsCached() {
 
 }  // namespace __sanitizer
 
-inline void *operator new(__sanitizer::operator_new_size_type size,
+inline void *operator new(__sanitizer::usize size,
                           __sanitizer::LowLevelAllocator &alloc) {
   return alloc.Allocate(size);
 }

compiler-rt/lib/sanitizer_common/sanitizer_internal_defs.h

@@ -191,15 +191,10 @@ typedef uptr OFF_T;
 #endif
 typedef u64  OFF64_T;
 
-#if (SANITIZER_WORDSIZE == 64) || SANITIZER_APPLE
-typedef uptr operator_new_size_type;
+#ifdef __SIZE_TYPE__
+typedef __SIZE_TYPE__ usize;
 #else
-# if defined(__s390__) && !defined(__s390x__)
-// Special case: 31-bit s390 has unsigned long as size_t.
-typedef unsigned long operator_new_size_type;
-# else
-typedef u32 operator_new_size_type;
-# endif
+typedef uptr usize;
 #endif
 
 typedef u64 tid_t;

compiler-rt/lib/sanitizer_common/sanitizer_placement_new.h

@@ -17,8 +17,6 @@
 
 #include "sanitizer_internal_defs.h"
 
-inline void *operator new(__sanitizer::operator_new_size_type sz, void *p) {
-  return p;
-}
+inline void *operator new(__sanitizer::usize sz, void *p) { return p; }
 
 #endif  // SANITIZER_PLACEMENT_NEW_H