Modify examples build file to avoid depending on transitive dependencies

In order to avoid impact from changing transitive dependencies, it is preferred to explicitly depend on the modules which are directly used in code. Examples build files do not seem to follow this pattern as discussed here:

https://github.com/apple/servicetalk/pull/754#discussion_r321468992

We should update the examples to declare explciit dependencies which are used in that example's code.

Start by reviewing the examples build files and the linked discussion in PR #754. Compare each example's declared dependencies with the modules used by its code, then verify that every directly used module is declared explicitly and that the examples still build.

Written by the indexing model from the issue text.