Bazel extractors: Emit .kzip files by default. (#3043)
Bazel extractors: Emit .kzip files by default. (#3043)

As part of #2867, switch the default format emitted by the Go-based Bazel
extractors to be .kzip instead of .kindex. This means the name of the tool is
now no longer accurate, but we can clean that up in a separate pass.
kythe/kythe,kythe/kythe,bzz/kythe,bzz/kythe,bzz/kythe,bzz/kythe,bzz/kythe,kythe/kythe,bzz/kythe,bzz/kythe,kythe/kythe,kythe/kythe,kythe/kythe,bzz/kythe,bzz/kythe,kythe/kythe,bzz/kythe,kythe/kythe,kythe/kythe,kythe/kythe,bzz/kythe,kythe/kythe,bzz/kythe