Improvements for tileset memory statistics

While working on #10397, I noticed a couple things that could be improved about tileset statistics:

1. Statistics distinguish between "loaded" counts (increment on tile load, decrement on tile unload) and "selected" counts (only counts visible tiles). However, this is not done consistently. E.g. points have both a load and a selected count, while triangles only have a selected count.
2. Statistics are not updated frequently enough for `ModelExperimental`. If the model was loaded, but then due to a configuration change the draw commands were re-built, the totals might change. These updates are not captured with the current timing.

The issue names tileset statistics, points and triangles, and ModelExperimental, but no files or tests. Start by tracing where loaded and selected counters are maintained and where ModelExperimental draw commands are rebuilt; done means the counters are updated consistently and totals refresh after configuration changes.

Written by the indexing model from the issue text.