Use pop-up drawer when interact with mobile app

**Describe the usability problem**
Currently when a mobile app connecting to Metamask Mobile, it has to jump to the Metamask Mobile app and sign the request. I think it could be simplified with one pop-up drawer to showcase those info and confirm the request. (Like Google Pay/Apple Pay)

**Expected behavior**
1. App created and request to connect to Metamask.
2. A pop-up drawer intent shown to user to confirm request.
3. Once it confirmed/rejected the request, send a callback to app.

**User impact | Usage frequency | Feasibility scores**
Not a important request, but it will surely improve the fluency of user experience.

Start by tracing how a mobile app connection request currently hands off to MetaMask Mobile. Compare that flow with the requested pop-up drawer: it should show request details, allow confirmation or rejection, and send the result back to the app.

Written by the indexing model from the issue text.