Do not execute dojo/on until DOM is ready

This ensures that the focusin/out feature detection operates
properly even when people do not follow best practices and put
their code in the <head> instead of before </body>.

Refs #17599.
Revert "Do not execute dojo/on until DOM is ready"

This reverts commit 08187b88273f09326e5ebc8ea03eecd592e7eaca.
fix regression introduced by #17155
Just use onfocusin as a detection test for focusin support

Due to various restrictions on what dojo/on can depend on,
and a desire to resolve this issue so that a release can be issued,
simply check for a matching event key on the has-test element.
This stops focusin/focusout from being used in WebKit and Blink
in lieu of event capturing, which is not ideal, but is not any
worse than what was happening before.

Refs #17599.
Add missing host-node and host-rhino rules to has.js

Fixes #17741.