This commit introduces a `SelectLikeOpInterface` that can be used to
handle select-like operations generically. Select operations are similar
to control flow operations, as they forward operands depending on
conditions. This is the reason why it was placed to the already existing
control flow interfaces.
This commit introduces a slicing utility that can be used to walk
arbitrary IR slices. It additionally ships logic to determine control
flow predecessors, which allows users to walk backward slices without
dealing with both `RegionBranchOpInterface` and `BranchOpInterface`.
This utility is used to improve the `noalias` propagation in the LLVM
dialect's inliner interface. Before this change, it broke down as soon
as pointer were passed through region control flow operations.
