Added steps for verifying logcat output and pushing files to the device

I added three methods to `operations.rb`:
1. clear_logcat: clears the logcat buffer to ensure clean tests
2. emitted_via_logcat: searches the logcat logs for a specific substring. Can filter by tag or level.
3. get_levels_emitted_via_logcat: creates a hashtable of log levels emitted along with priority. Useful for verifying log filtering features in an app.

I also added a step for pushing a test file to the device.