[WinEH] Ignore lifetime.end PHI nodes in empty cleanuppads

This fixes a bug where a PHI node that is only referenced by a lifetime.end intrinsic in an otherwise empty cleanuppad can cause SimplyCFG to create an SSA violation while removing the empty cleanuppad. Theoretically the same problem can occur with debug intrinsics.

Differential Revision: https://reviews.llvm.org/D72540