[llvm] [RISCV] Separate the analysis part of RISCVInsertVSETVLI. (PR #149574)

[Mikhail Gudim via llvm-commits]

mgudim wrote:

I realise it's a huge diff, but it is very mechanical: just moved functions to a different place. Also this is pretty hard to split, since if a function is moved all the other function called by it have to be moved as well.

Let me know if you think this should be broken down into more commits.

https://github.com/llvm/llvm-project/pull/149574