SystemServer: Add trunk stable to dumpsys info

Example of the output after this CL (flag are alphabetically sorted):

```
🚩Flag dump:
        [ ]: aCoolFlag
        [ ]: anotherNiceFlag
        [■]: woawThisFlagIsEnabled
```

Bug: 321313362
Fix: 321313362
Flag: Exempt, debug tool that is protected by a complete try catch
Test: m Bluetooth
Test: adb shell dumpsys bluetooth_manager | Then check that your flags
      are correctly displayed (and with the expected value)
Change-Id: I4ec9d40d46b7c983ce1be90d95e72a954f63e540