Add support to allow Clickable to autofill password prompts on devices when using SSH

Currently, Clickable prompts for the password on every command when using SSH, which involves re-entering it many times throughout the course of a build. This PR introduces an optional --password argument, which uses sshpass to autofill these prompts to avoid repeatedly asking the user on each command.

This is an entirely optional flag, and does not break any existing workflows if this flag is omitted. It does add a dependency for sshpass on the host machine, but this PR includes checks to ensure that it is present on the host system before attempting to enable this functionality (which prevents any breaking changes from being introduced on systems that do not have sshpass installed). If sshpass is missing on the host system, the --password flag will simply be ignored, and the user will be displayed a friendly warning to notify them.