refs: https://github.com/TryGhost/Toolbox/issues/146
Switched to @tryghost/logging instead of passing around the library. The main sticking points of this change are jobs. When jobs are launched we don't want them to use a separate @tryghost/logging instance because they would start parallel rotation jobs. @tryghost/logging v2.x passes all logs to the parent process if run in a child process, so that we can use the same patterns in jobs and the rest of the codebase.
- core/shared/i18n is no longer used. Remove it to prevent temptation!
- this class needs merging with the one in themes, but for now just co-locate them as that's quicker and easier
