Revert "Add dependency visiting methods to BottomUpMutatorContext"

This reverts commit a2b2080f.

Dependency visiting methods conflict with the dependency adding methods
already present on BottomUpMutatorContext - mixing calls to visit
dependencies and adding dependencies produces requires hard-to-define
semantics, and complicates parallizing mutators.

Change-Id: I2f793c8db45b97f4d79badc9fe88315fe38d90cd