[Jetchat] Add Nested scrolling interop API

[simona-anomis]

Add the Nested scrolling interop API to Jetchat Profile screen, to showcase the proper usage of this experimental API in the scenario of having a View parent and a composable child. Steps done:

• Refactor ProfileFragment to use an old school XML layout, with a CoordinatorLayout, CollapsingToolbarLayout that hosts a ComposeView for the JetchatAppBar composable and a separate ComposeView that will host the ProfileScreen composable
• Set the correct Fragment layout and composables using the guidelines on View/Compose interoperability
• Hook up the nested scrolling interop connection between the View parent and composable childeren via rememberNestedScrollInteropConnection() to enable the collapsing behavior and scrolling connection between all these elements
• Minor clean up

More elaborate documentation on this coming soon on http://developer.android.com/

[astamato]

Nice one!