Refactor to have a "cf" function which assumes you are running "cf"

This allows us to only specify the name of the cli binary in one place

Signed-off-by: Ruth Byers <rbyers@pivotallabs.com>
Allow `cf` command name to be specified from outside `command_runner`

[#67166618]

Signed-off-by: Ruth Byers <rbyers@pivotallabs.com>
Allow `cf` command name to be specified when executing canaries

- Moved default out of `command_runner` to `cli` because that is where other defaults are
- This doesn't do anything yet; the default behavior is still the same as before

[#67166618]

Signed-off-by: Ruth Byers <rbyers@pivotallabs.com>
Allow `cf_command` to be specified when invoking `canaries`

[#67166618]

Signed-off-by: Ruth Byers <rbyers@pivotallabs.com>