[llvm] [GlobalISel] use constexpr LLT types when creating ISel data (PR #191574)

[David Green via llvm-commits]

https://github.com/davemgreen commented:

I was thinking that all the types should be using the low level constructors, including float versions. At some point in the future, because we have targets that do not enable ExtendedLLT, the float32() and similar functions might need to generate scalar types too. We can fix this in the future if it comes up though.

https://github.com/llvm/llvm-project/pull/191574