Improve arg parsing for `cmd power set-wakelock`

- Make `-d` actually optional and reject unknown options
- Make wakelock type required instead of causing NPE

Bug: 435557564
Test: cmd power set-wakelock acquire PARTIAL_WAKE_LOCK
Test: cmd power set-wakelock acquire -d 0 PARTIAL_WAKE_LOCK
Flag: EXEMPT shell command only
Change-Id: I62f8b9db34f7d74e3453eaf8db63c7885c2c84f4