Ensure autofocus for dynamically-created panels, sections, and controls

[westonruter]

At the moment, autofocus via URL params (#28650) only works for panels, sections, and controls which are defined statically up-front. Any constructs not created statically will be stripped from exporting to JS. Additionally, from the JS side, if any of these constructs do not exist by ready, they will also be ignored.

Autofocus should work for anything that gets created with JS.

[westonruter]

See 36018.0.diff​.

The PHP logic for calculating $can_autofocus is being over zealous in its checks. If the panel, section, or control doesn't exist on the JS side (due to not existing or due to a capability failure), there will not be anything to focus on.

[westonruter]

Clean up comment

[westonruter]

Further simplify

[westonruter]

In 36796:

Customize: Ensure autofocus deep-linking applies for dynamically-created panels, sections, and controls.

Removes overly-zealous filtering of autofocus panels, sections, and controls which are unrecognized or for which the user doesn't have the capability to focus (in which case it would no-op anyway). Also defers autofocus logic until instances are created, even after initial ready event. This ensures that autofocus can apply for any panels, sections, or controls that get created via the loaded preview.

See #28650.
Fixes #36018.