BTM shim: Use LE link for GATT and HID if LE is connected

When we connect to GATT and HID, we need to decide which transport to
use. If LE is already connected, use it. Otherwise use the device type
from storage (to be implemented).

Tag: #gd-refactor
Test: With HOGP device
Test: cert/run --host
Bug: 158861440
Change-Id: I618d4a42eb68a496d8764d7f5ecee1529603165b