Add port parameter

[KamilKurde]

The problem

Currently, this action uses ADB commands without specifying device/emulator to use. This is fine for GitHub-hosted machines, as they are isolated from each other, but becomes a problem when using this action on self-hosted machine, as ADB commands will fail if there are multiple devices present, and it wasn't specified which one to use.

The fix

Adding emulator-port input, that allows a job to specify port to start emulator on. This way, one machine could have up to 16 emulators running at the same time (due to constraints in port range) without interfering with each other.