RootCanal: Implement rootcanal_ll_test

This change adds a python binding for the DualModeController
class to enable isolated LL+HCI tests on one controller
instance.

Implement test LL/DDI/SCN/BV-13-C test from Bluetooth controller
certification test suite.

Test: atest --host rootcanal_ll_test
Change-Id: Ica6e856247b88fc03b1e205d33bf6d9f822327de