enhancement: add composition feature on intents

[gregorylegarec]

This PR adds intent composition feature. It allows, from an intent service, to request another intent. As this intent have to be handled by the intent client, due to X-Frame-Options limitations, it has been named Intent Composition.

An intent composition can be called this way:

const service = cozy.client.intents.createService()
// ...
const app = service.compose('INSTALL', 'io.cozy.apps', { slug: 'drive' })

What happens internally:

• The service send a compose message to the client
• The client handle this message, start a new intent and hides the current one
• Once the intent is resolve, it passes the result to the first intent, via a message to the service
• The service is resolved.

This process can be chained indefinitely.

Refactoring

I managed to refactor a little bit the code. What I had in mind was more modular and more clear than the actual result. I am not satisfied by the client part. But the code related to the composition is actually relatively simple and clear. I plan to improve the whole intent code base in the future.

[gregorylegarec]

(5) [COL] ETU je peux installer/configurer UN connecteur depuis de l'inter-apps [3]

[CPatchane]

Thanks @gregorylegarec 🏒