update Dashboard command to support passing a dashboard name as an argument

[kaidaguerre]

steampipe dashboard should be modified to accept a positional argument that can be the name of a dashboard or benchmark.

if the argument is passed then steampipe should run the dashboard (or dashboard view of benchmark) and then exit

steampipe dashboard should add an --output option. Initial values are: snapshot

inputs may be passed to dashboard via one or more --dashboard-input arguments.

the syntax is the same as --var

--dashboard-input=vpc_id="vpc-123456789012"
--dashboard-input='mandatory_tags=["Owner","Application","Environment"]'

Ideally, we will prompt for any missing inputs. If that is not viable, then we should minimally fail immediately and inform the user that the inputs must be specified.