Need to fail-fast on deprecations

[EricCousineau-TRI]

Deprecations generally slip through, and cause breakage when their removed.

[jwnimmer-tri]

I broke drake-external-examples master again because of this via https://reviewable.io/reviews/RobotLocomotion/drake/12680. Drake removed a deprecated text_logging_gflags header, but it remained used by drake-external-examples until it was fully removed and thus broke the build.

[EricCousineau-TRI]

Per f2f: C++ should be easy (-Wdeprecations or what not), if we're not already doing that.

For Python, will be annoying (env vars with test runners, updating each testing mode, or parsing stdout), but doable.

[jwnimmer-tri]

Note that we can't just turn on -Werror -- these repositories are intended for users to copy into their own project, and we don't want them using -Werror. So the trick is to find a way for us to get CI reports about these, but for that not to propagate that into users' replicas of this.