Bepu - Improve physics queries page

[ferafiks]

The physics queries page has a couple of problems:

• Currently it mostly consists of a bunch of random examples that aren't that well organized
• Missing dedicated explanations on most queries
• Missing explanation on stackalloc
• The name "physics queries" is a bit more difficult to find than "raycasts" or "raycasting". Separating the page into smaller sub pages for raycasting, sweepcasting and overlap would improve visibility

[VaclavElias]

The Bepu Physics docs were put together fairly quickly so we'd have at least a basic starting point now that Bepu is already implemented. Some areas are still missing or incomplete (for example, Constraints).

The main reason is simple: we don't have many dedicated technical writers at the moment, and most contributors have been prioritizing more urgent tasks. Community help would be hugely appreciated 💪🙂 even small additions or fixes make a real difference.