Expose and warn about Node Filters in Scene Tree Dock

[Mickeon]

Continuation of #65352. (see also #65352 (review))

This PR adds "Filter by Type" and "Filter by Group" in the Scene Tree Dock's MenuButton (the one on the top right featuring 3 dots), exposing them to everyone that doesn't religiously look at this engine's source code.

Menu	Tooltip
	Hovering on them displays an useful tooltip.

Behavior	Warning
When clicking on either of these, the matching parameter is appended to the terms, and the caret is automatically brought to the end.	When typing a filter that cannot be identified, a warning icon is displayed. The reason is explained in the tooltip. Before this, the temporary solution of #65352 is to spam warnings to the console.

And lastly, the same options are also quickly available by right-clicking or middle-clicking in the text field.

Right Click	Middle Click

[akien-mga]

Looks good, but the warning system is weird that it shows a warning icon but the actual warning is shown in the menu. That's not something we do anywhere else in the editor.

The warning should be shown in a tooltip on hover of the warning icon, like for node configuration warnings.

[Mickeon]

The warning should be shown in a tooltip on hover of the warning icon, like for node configuration warnings.

Not sure it would be possible to have the tooltip display exactly there, without resulting into something poor and hacky. I want to note that the Warning icon in this PR is actually still the "clear" TextEdit button. Its behavior remains unchanged, which means it would clear the text on click instead of telling the user what's wrong. Not the worst thing in the world, really, just putting it out there.

[Mickeon]

Going to update this PR to display the warning as a tooltip hovering over the filter TextEdit:

Takes a while to show up by default, but it is how it is with tooltips.
(Added an ending "." at the end of that warning, too)

[Mickeon]

All good now, I hope.

[KoBeWi]

I have nodes without any groups. With empty group: filter, some of them disappear:

Why is that?
EDIT2: Same happens when I filter with group:c, where c can be any character EDIT3: The latter does not happen if any node has a group.

EDIT:
Ok maybe groups are not related to this PR. I think it just finds some groups that aren't displayed in the editor. Maybe we could ignore them.

EDIT:
Right-click options do not work:

[Mickeon]

Thank you for the testing as always, @KoBeWi. The group thing may not be related to this PR, but it'd still be nice to see if something can be done about it, because I implemented the feature and it'd be nice to address it. It may be related to the way groups are detected. Unfortunately it has to be a bit finnicky already because Groups don't seem to distinguish between internal and exposed. It'd love to take a look at that project you're testing it with to spot the issue.

Meanwhile, I addressed the right-click options not working.

[KoBeWi]

Groups don't seem to distinguish between internal and exposed. It'd love to take a look at that project you're testing it with to spot the issue.

"Exposed" groups have persistent flag enabled. I think in your case you can use get_persistent_group_count() method and check if it's non-zero.

[Mickeon]

Ok I can address it in another PR. Perhaps within #65939 to make it quick.

[akien-mga]

Thanks!