tests: Bluetooth: CAP: Modify initiator unittests to native_sim

Modify the unit tests to use the native_sim board instead of the
unit_testing board.
The native_sim board allows us to use the kernel in a more
regular way, while still being able to treat the tests as
unittest.

To support mocking we cannot rely on the default
Kconfig options and values. The required Kconfig options
to satisfy dependencies are overridden in the Kconfig
file and the necessary Kconfig files are sourced.
We cannot enable e.g. CONFIG_BT as that would attempt
to pull in a lot of files we do not want in this test.

This commit also removes unused includes in the CMakelists

Signed-off-by: Emil Gydesen <emil.gydesen@nordicsemi.no>
11 files changed