Zello PTT Custom Button - Fast

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New Features:
- Allow to open Voiceping from the lock screen
- Open lock screen after reboot
- Upgrade billing lib to version 4

Bug fixes:
- Fix sometimes channel is not updating on some cases
- Fix sometimes cannot change volume
- Faster volume adjustment
- Fix weird behavior when volume key is already assigned
- Fix several crashes
- Fix app cannot detect Voiceping on Android 11 or above