x/devtools: Add Mojo Profile version 7
x/devtools: Add Mojo Profile version 7

In this profile:
- kiosk_wm was replaced with several other window manager services.
- The Dart Service Describer was added to Mojo's Dart API.

MultiPart: 1/3

Change-Id: I9f143e8678159627783a56e59f4f21b633cf6bed

vanadium/go.devtools,vanadium/go.devtools,vanadium/go.devtools