hle: Type check ResponseBuilder::Push arguments, and fix use in vi.cpp

- Add a type check so that calling Push with an invalid type produces a
  compile error rather than a linker error.

- vi.cpp was calling Push with a variable of type `std::size_t`.
  There's no explicit overload for `size_t`, but there is one for `u64`,
  which on most platforms is the same type as `size_t`.  On macOS,
  however, it isn't: both types are 64 bits, but `size_t` is `unsigned
  long` and `u64` is `unsigned long long`.  Regardless, it makes more
  sense to explicitly use `u64` here instead of `size_t`.

src/core/hle/service/vi/vi.cpp

@@ -1230,8 +1230,8 @@ private:
         const auto height = rp.Pop<u64>();
         LOG_DEBUG(Service_VI, "called width={}, height={}", width, height);
 
-        constexpr std::size_t base_size = 0x20000;
-        constexpr std::size_t alignment = 0x1000;
+        constexpr u64 base_size = 0x20000;
+        constexpr u64 alignment = 0x1000;
         const auto texture_size = width * height * 4;
         const auto out_size = (texture_size + base_size - 1) / base_size * base_size;