Support modifier key and duration for keycombination command

The keycombination command allows user could send the combination keys
via shell. This CL would allow the modifier key (ctrl, alt, shift, meta)
could update the meta state for the following keys.

This CL would also support the new argument (-t) to allow user could
specify the duration of the combination key pressing.

Bug: 204831125
Test: adb shell input keycombination CTRL_LEFT A
Test: adb shell input keycombination -t 3000 VOLUME_DOWN VOLUME_UP
Change-Id: I48fa398e310d245db270b500bd3eac1655f23b49