SystemServer: Add snake case flag in dumpsys

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

```
🚩Flag dump:
        [ ]: aCoolFlag             a_cool_flag
        [ ]: anotherNiceFlag       another_nice_flag
        [■]: woawThisFlagIsEnabled woaw_this_flag_is_enabled
```

Bug: 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: I47547c6a228b54a7dfa41a97bb815eb614b541c7