tvix: Bring back log verbosity

#76
Opened by glittershark at 2020-11-18T14·43+00

  1. https://cl.tvl.fyi/c/depot/+/2134 starts this.

    glittershark at 2020-11-22T22·25+00

  2. We should also add the --verbose and --quiet options back into the global option parsing code, as these were removed during the glog conversion, which has caused issues e.g. in https://b.tvl.fyi/issues/78

    multi at 2020-11-22T23·24+00