Make change detection clamping docs more accessible

[Nilirad]

How can Bevy's documentation be improved?

For how change detection is currently implemented, there is a far-fetched technical limitation to it. This is already documented in the public constants CHECK_TICK_TRESHOLD and MAX_CHANGE_AGE, located in bevy_ecs::change_detection, but there are some issues with it:

• Those constants are quite hidden, and they only seem public for the doc comments
• The doc comments refer to check_tick, which is a private function, therefore confusing for users who don't know about the implementation details.

Proposed solution

The constants should be made private, and their documentation should be moved to the bevy_ecs::change_detection module level. They should also be adapted to be understandable to people who don't know the implementation details of change detection.

Since the module is practically undocumented, having a brief intro of what change detection is in Bevy, and how it can be used (i.e. by using the change detection filters), would be very appreciated, but not strictly necessary.

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See also

• [Merged by Bors] - Make change lifespan deterministic and update docs #3956