[mlir][Inliner] Add a `wouldBeCloned` flag to each of the `isLegalToInline` hooks.

Often times the legality of inlining can change depending on if the callable is going to be inlined in-place, or cloned. For example, some operations are not allowed to be duplicated and can only be inlined if the original callable will cease to exist afterwards. The new `wouldBeCloned` flag allows for dialects to hook into this when determining legality.

Differential Revision: https://reviews.llvm.org/D90360