[AA] Remove CFL AA passes

The CFL Steens/Anders alias analysis passes are not enabled by
default, and to the best of my knowledge have no pathway towards
ever being enabled by default. The last significant interest in
these passes seems to date back to 2016. Given the little
maintenance these have seen in recent times, I also have very
little confidence in the correctness of these passes. I don't
think we should keep these in-tree.

Differential Revision: https://reviews.llvm.org/D139703