Bluetooth: Add config to select Rfcomm services

We don't need Dev-kit's all Rfcomm services to be running every time.
Add config option for tests to select Echo, MAP or PBAP Rfcomm services.
Default to Rfcomm Echo service, if not specified.

BUG=b:424465503
TEST=Run BeTo test_concurrent_connections test

Change-Id: I5700d270b048276091daf3fae10e1df9bd53776a
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/chameleon/+/7115464
Commit-Queue: Manish Mandlik <mmandlik@chromium.org>
Reviewed-by: John Lai <johnlai@google.com>
Tested-by: Manish Mandlik <mmandlik@chromium.org>