DND mode: Add dnd mode for v8

[FeelyChau]

Change-Id: I869a75c51ee6e6c65e82c62304f58925f84196af

Add week days support for DND mode, this pr is not finished for now. There are still 4 more things to do:

• [x] 1. Broadcast the message to enter or exit DND mode;

• [ ] 2. Implement the volume manager to save or set volume for DND mode;

• [ ] 3. Implement the timezone(from user's location) synchronization for system clock;

• [x] 4. Add tests.

Checklist

• [ ] npm test passes
• [ ] tests and/or benchmarks are included
• [ ] documentation is changed or added

[rokidbot]

Can one of the admins verify this patch?

[legendecas]

Closed due to inactivity. Reopen it if necessary.