Better output in headless mode

The output log while loading a scene (and therefore loading octree, regions, entitites, chunks, ...) [might confuse some users](https://github.com/chunky-dev/chunky/issues/1322#issue-1281488036), because it does not always update its progress after completing a specific step.

Some things I'd like to work on:
- reworking the task tracker and progress tracker to be used in GUI and log (very tightly coupled to different systems right now)
- flag to disable headless output refreshing (not overwriting the last line of output, therefore creating new lines every time something happened)
- fixing inconsistent log spacing, messages and errors