Tilemap chunk update has ambiguous scheduling

[tbillington]

TilemapChunks are updated once per frame in update, however the system is not in any system sets not is it public so it can't be scheduled around in user code. This results in it potentially being scheduled at any point in Update causing potentially one frame late delays or not depending on the whims of the scheduler.

Reported on discord by user weykent https://discord.com/channels/691052431525675048/691052431974465548/1448481798211502220.

The workaround they're currently using is copying the system code into their own project and adding it a second time scheduled after their systems.

[alice-i-cecile]

Just making this public is the easiest solution, but I'd approve a public system set if there's a good reason to encapsulate this.