[llvm] [RFC][GlobalISel] Use Builders in MatchTable (PR #65955)

[Pierre van Houtryve via llvm-commits]

Pierre-vh wrote:

I reverted the observer changes, so now it's just adding the MachineIRBuilder and nothing else changes pretty much.
It's all I need to implement the other patches in this series

https://github.com/llvm/llvm-project/pull/65955