cleanup functional tests and update unit tests

[KazuCocoa]

I wanted to do cleanup to reduce unnecessary e2e test's flakiness before when I moved to GHA from Azure.

Moving client-side check to unit rather than functional. The functional one will have minimal check as the client's for example appium server staring check.

Example usage is sufficient in the unit test's code example. The functional directory can have more less code as this project because this project does not check driver side.

Also, it would be nice to create unit tests for each module to test them out for Android/iOS etc separately.