An attempt to remove all 12 remaining internal routes mentioned in the issue, including all the code that these removals render dead.
I did this because @keegancsmith's call for "some tasty red diffs" made it irresistible for me.
I'm not very experienced in Go, though: I only did two smaller projects when I joined Sourcegraph. I ventured this because I have extensive refactoring experience, and I use IntelliJ IDEA, which provides a very safe setup for me to do such changes.
I'd feel confident that my changes are safe, but all the tests are failing on it. (Tried to re-run, same result.) It's weird, though, that so many tests are failing, and I've found our CI to be a bit unreliable lately, so the changes might just as well be fine.
I need a comprehensive review on this, though.
Feel free to throw away this code if the review takes more time for someone than just doing the changes. Also, feel free to mix and match my changes into another PR if my changes are just partially helpful.
Test plan
Check the code and see if it makes sense. I pushed it as 11 separate commits to make a deep core review easier, but as the changes are similar, just a review of the final state might be enough. Whichever makes more sense.
