Allow debug logging that can be enabled / disabled

Use case

In the text app we sometimes need very detailed logging. Think several lines of debug logging per keystroke.

Currently we have some logging statements commented out that we enable then.
But if they were always enabled that would spam the logs too much.

Would be nice to have this build into the logger.

Possible interface

// ExampleService.ts in the text app
const logger = getLoggerBuilder().setApp('text')... .build()
const debug = logger.createOptionalDebugLogger('ExampleService')
...
service.on('update', (update) => debug('received update', { update }))

Usage in the Browser console:

OCA.Logger.debug.text.ExampleService = true

Populating OCA.Logger.debug when the optional debug logger is created would enable auto completion on the browser command line.

The issue names getLoggerBuilder(), createOptionalDebugLogger(), and OCA.Logger.debug; start by tracing those entry points in the TypeScript logger implementation. Confirm how optional loggers should expose their app and service keys and how the browser toggle controls output. Done means the proposed API works without default debug spam and the browser console object is populated for autocomplete.