Most of the custom logic to handle special keying cases is now inside
the AnimationPlayerEditorPlugin.
The EditorInspector now emits a signal when inspecting a new object.
The second parameter of the signals `EditorInspector.property_keyed` and
`EditorProperty.property_keyed_with_value` can be NIL, causing the event
to fire with less arguments when using `emit_signal` that accepts
Variant arguments, so we use the pointer version instead.
For the time being we don't support writing a description for those, preferring
having all details in the method's description.
Using self-closing tags saves half the lines, and prevents contributors from
thinking that they should write the argument or return documentation there.
We already removed it from the online docs with #35132.
Currently it can only be "Built-In Types" (Variant types) or "Core"
(everything else), which is of limited use.
We might also want to consider dropping it from `ClassDB` altogether
in Godot 4.0.
Follow-up to #31925, `<member />` tags just before `</members>` would cause
a parsing issue, and we'd never notice that we're no longer parsing members.
Also added space before closing `/>`.
