An empty struct without a deinit gets a single bit which is used to
track the struct's liveness. Previously, an empty struct with a deinit
also only got a single bit. Consequently, when discarding the struct
(i.e. dropping the deinit), there was no bit left to represent the
struct. This resulted in a failure to track liveness for the value.
rdar://126863003
Before move-checking values, complete the lifetimes of all the values
derived from them via copy, borrow, and move.
Collect all such values and their derived transitive values and then
complete the lifetimes of each, visiting the instructions which produce
them in post-order.
Once OSSALifetimeCommpletion runs as part of SILGenCleanup, this code
can be deleted.
