Accept non-standard bools in more CUDA kernels

This fixes all remaining CUDA kernels, except those using `cub` or
`thrust`, to accept boolean tensors with values other than 1 or 0.

I do this by using `c10::load` in more places, and also adding a
`load_vector` helper into `MemoryAccess.cuh` that does the same thing
for vectorized loads.

Pull Request resolved: https://github.com/pytorch/pytorch/pull/78957

Approved by: https://github.com/mruberry

c10/util/Load.h

@@ -16,6 +16,7 @@ template <>
 struct LoadImpl<bool> {
   C10_HOST_DEVICE static bool apply(const void* src) {
     static_assert(sizeof(bool) == sizeof(char), "");
+    // NOTE: [Loading boolean values]
     // Protect against invalid boolean values by loading as a byte
     // first, then converting to bool (see gh-54789).
     return *reinterpret_cast<const unsigned char*>(src);
@@ -29,4 +30,9 @@ C10_HOST_DEVICE T load(const void* src) {
   return c10::detail::LoadImpl<T>::apply(src);
 }
 
+template <typename scalar_t>
+C10_HOST_DEVICE scalar_t load(const scalar_t* src) {
+  return c10::detail::LoadImpl<scalar_t>::apply(src);
+}
+
 } // namespace c10