Debug label not intuitive, should be log prefix?

### Expected Behaviour
`test.js`:
```
const logger = require('@adobe/aio-lib-core-logging')('myapp', { provider: './DebugLogger' })
logger.debug('yo!')
```

`DEBUG=myapp node test.js` => should print `yo!`

### Actual Behaviour
Need to add a `*` to the DEBUG env var
`DEBUG=myapp* node test.js` => prints `yo!`

This is because the debug label is extended with action name and log level

suggestion: preserve the user given debug key but add a string prefix to each log message