Rollup merge of #144775 - lcnr:skip_binder-comment, r=BoxyUwU

more strongly dissuade use of `skip_binder`

People unfortunately encounter `Binder` and `EarlyBinder` very early on when starting out. In these cases its often very easy to use `skip_binder` incorrectly. This makes it more explicit that it should generally not be used and points to the relevant `rustc-dev-guide` chapters.

r? `@BoxyUwU`

Author: tgross35