Added utility function for invoking Prompting.Host.
Added utility function for invoking Prompting.Host.

This commit adds a utility function for hosting a prompter via the
Prompting.Host method. Although Prompting.Host can be used directly, it
is slightly complicated and the typical use case is just hosting a
prompter. This utility function should make it easier to adapt command
prompting.

Signed-off-by: Jacob Howard <f862f167b85d41b225785c70d70808bc7337c1fe@havoc.io>

havoc-io/mutagen,havoc-io/mutagen