Remove support for bazel builds

[dnovillo]

We used to need bazel support at Google, but that is no longer the case. @chaoticbob any concerns with removing it? Are there any downstream users who rely on it?

[chaoticbob]

No concerns on my end. I can't be for sure if downstream users but I suspect bazel users aren't numerous. I think it's safe to remove. We'll take feedback if it turns out to be problematic for someone.

[dnovillo]

SG. PR coming up.