unit_testing board `select`s deprecated `NATIVE_APPLICATION`

[Thalley]

Describe the bug

When building a unit test for the unit_testing board there is a warning:

warning: Deprecated symbol NATIVE_APPLICATION is enabled.

since the unit_testing board select NATIVE_APPLICATION in https://github.com/zephyrproject-rtos/zephyr/blob/main/subsys/testsuite/boards/unit_testing/unit_testing/Kconfig.unit_testing

NATIVE_APPLICATION was deprecated in #81232 and should not be used in Zephyr.

Regression

• This is a regression.

Steps to reproduce

Can be reproduced by building any test that uses the unit_testing board (has type: unit), e.g.

scripts/twister -T tests/bluetooth/audio/ascs

Relevant log output

Building the above should show something like

warning: Deprecated symbol NATIVE_APPLICATION is enabled

in e.g. twister-out/unit_testing_unit_testing/host/tests/bluetooth/audio/ascs/bluetooth.audio.ascs.test_unicast_client_enabled/build.log

Impact

Annoyance – Minor irritation; no significant impact on usability or functionality.

Environment

OS: Linux
Commit SHA: 6559c7f

Additional Context

No response