[scenic] Move scenic_tools to shell binaries

Remove them from deprecated_system_image, make them deployed as shell
binaries instead.

TEST=Run `fx serve`. Run `set_root_view`. Modify `set_root_view` in a
user-visible way and build. Confirm that `set_root_view` now runs with
the updated code, without needing to repave.

Change-Id: I4c86efbfcf3bbdbd77d9579a4f02344c5c8192ba
1 file changed