Combine `x86_64-qnx` and `unit-tests-x86_64-qnx` into one config

### What

#328 introduced a separate Bazel argument for QNX QEMU unit tests, to work around the unit test framework needing `--run_under`, which interferes with the integration tests.

It would be nice to run all tests in one command.

### Acceptance Criteria (DoD)

- QNX unit tests and integration tests can both be run under QEMU in one invocation of `bazel test`

### How

Follow the guide in the unit test framework to use wrapper targets rather than `--run_under`, then resolve the errors that leads to.

Start with the Bazel configuration and arguments introduced by #328, then follow the unit test framework guide on using wrapper targets instead of --run_under. Run the QNX unit and integration tests under QEMU with one bazel test invocation, resolve the resulting errors, and verify both test groups pass together.

Written by the indexing model from the issue text.