[llvm] [mlir] [mlir] Move InlinerInterface from Transforms to Interfaces. (PR #84878)

[Stella Laurenzo via llvm-commits]

stellaraccident wrote:

I hear the "header only dep" argument but it still makes me quite uncomfortable as it represents project organization lines that should not be crossed: we have got to start thinking of some of these pieces as distinct projects.

https://github.com/llvm/llvm-project/pull/84878