tests: kernel: mutex: move race timeout test to mutex_api

Previously, this change was added to `mutex_error_case`.

That worked fine in `main`, but once the change was backported to
`v2.7-branch`, the test would fail because it *did not* cause a
failure. The reason for that, was that the `mutex_error_case`
suite has `CONFIG_ZTEST_FATAL_HOOK=y`.

With the newer ztest API, it allowed a separate suite to be used,
allowing the test to pass (although it did not really fit in with
the rest of the testsuite).

The solution is to simply merge it with the `mutex_api` suite
which uses non-inverted success logic.

This change will also have to be cherry-picked for the backport
in #49031.

Fixes #48056.

tests: kernel: mutex: move race timeout test to mutex_api

Previously, this change was added to `mutex_error_case`.

That worked fine in `main`, but once the change was backported to
`v2.7-branch`, the test would fail because it *did not* cause a
failure. The reason for that, was that the `mutex_error_case`
suite has `CONFIG_ZTEST_FATAL_HOOK=y`.

With the newer ztest API, it allowed a separate suite to be used,
allowing the test to pass (although it did not really fit in with
the rest of the testsuite).

The solution is to simply merge it with the `mutex_api` suite
which uses non-inverted success logic.

This change will also have to be cherry-picked for the backport
in #49031.

Fixes #48056.

Signed-off-by: Chris Friedt <cfriedt@meta.com>