[DevTools] Refactor connection-related classes.
Extracted small connection interface, it's params and factory.
Supported connect/disconnect for all main connection types.
Renamed previous Connection to TargetPrototype, which will be merged to Target soon.
BUG=
648775
Committed:
https://crrev.com/6274a2d207fc8383d1182204b2a900d80c3d3f0e
Cr-Commit-Position: refs/heads/master@{#427521}