Make a11y traversal documenation clearer

- Add clearer phrasing and give an example that explicitly uses the
  method
- Soften the language, since it's the screen reader that ultimately decides traversal order.
- Add a note that recommends not using this API
- Add a suggesting to avoid loops
- Add a bit about importantce in the attr documentation

Bug: 280091061
Test: n/a (documentation change)
Change-Id: I792f72354664cb0b04696d716118f96980721d23