[cli] Add Commands to create an application from an archetype

[eolivelli]

Summary:

• add langstream archetypes get command
• add langstream archetypes create-application command
• fix the sample archetype (default values of secrets cannot be read from the ENV, as the deploy application command basically runs on the control plane and not locally)
• add a sample JSON file with the parameters corresponding to the demo archetype bundled with LangStream