Examples and/or documentation for running iOS tests on a physical device

I've been using `rules_apple` successfully for a few projects and can run `ios_unit_test` in a simulator. However, there doesn't seem to be much documentation regarding how to run tests on a physical device. A great use case would be to easily measure on-device performance.

It would be tremendously helpful to have at least some documentation, if not working examples under the `//examples` directory.

I'm imagining something along the lines of:
* How to run a single `ios_unit_test` and `ios_ui_test`.
* How to run `ios_unit_test_suite` and `ios_ui_test_suite`.
* Examples of different `runner`s and `test_host`s and what they mean.
* What's required in a host `ios_application`.
* Tulsi example.
* How this all fits with [google/xctestrunner](https://github.com/google/xctestrunner).

Start by reviewing the existing documentation and the //examples directory for ios_unit_test, ios_ui_test, ios_unit_test_suite, and ios_ui_test_suite. Compare the requested runner and test_host cases, Tulsi, and google/xctestrunner integration, then document or add examples that cover physical-device execution and define what host ios_application configuration is required.

Written by the indexing model from the issue text.