[compiler-rt] [compiler-rt] Simplify and rename of operator_new_size_type (PR #83912)

[Alexander Richardson via llvm-commits]

arichardson wrote:

> > What is size_t on 32-bit windows?
> 
> It seems to be `unsigned int`.

I just looked at this in godbolt and it seems like it should work as intended on MSVC 32-bit: https://godbolt.org/z/3KT59qKoh Do you build with any special flags that could affect this?

https://github.com/llvm/llvm-project/pull/83912