External trigger handling

[zjn0505]

Currently in this workflow adb external trigger is used internally and exclusively for the last step trigger in apk hotkey, to invoke "apk installation from" with given apk file.

The ideal flow should be.

• Expecting func argument in adb external trigger.
• If there is one received, ”Show devices options“ step should be bypassed after selecting connected device. and target function should be invoked based on func arg.

This feature will be helpful for requirements like #10