`brew cask list` supports the `--full-name` flag which will include the tap
name for casks not part of the core caskroom/cask tap. For example, if
cask "foo-beta" is installed from the caskroom/versions cask, `brew cask
list --full-name` will report the name as "caskroom/versions/foo-beta".
Remove pending tests that are never run on CI (i.e. require `--online`),
remove fixtures for those tests and just make `--official-cmd-taps`
run by `--online` instead.
Remove `testbottest` formula (this should have lived in the `brew
test-bot` repository from the outset) and make various other changes to
fix the Linux build here.
