Rig TransitiveAddressWalker to keep track of enough information for passes to
correctly check for pointer escapes and dependence uses. Requires for precise
bail-outs and asserts.
The extra complexity for traversing phis is not needed now that it handles
borrowed-from instructions. Remove the redundant logic because it complicates
the liveness algorithm and generates confusing results.
When visiting consumes, also visit `extend_lifetime` instructions.
These instructions are not lifetime ending, but together with the
consumes, they enclose the users of a value.
Add a flag to LinearLiveness to control whether these instructions are
added so that the verifier can use verify that all such instructions
appear outside the linear lifetime boundary (not including them).
Encapsulate all the complexity of reborrows and guaranteed phi in 3
ownership liveness interfaces:
LinerLiveness, InteriorLiveness, and ExtendedLiveness.
