Add a name for the packed scene preview in inspector

[brantkings]

An idea that I think will improve the editor a bit. I don't think this is high priority or anything. But I also think it might be easy to implement!

When you look into the packedscene preview, you initially get this on an empty scene:

But as soon as the AABB gets different than 0,0,0 (say, I've put some Marker3Ds around), it changes to this:

And I have to hover over the scene to know which is it, it is kinda cumbersome to do when verifying a lot of nodes with the same code, for example.

Can't it be like this, or we have an option that enables this (maybe there is already but couldn't find it!):

Sorry for terrible mouse handwriting! But the idea is to be able to see its name in a glance!

[Calinou]

• Related to Remove scene previews in the inspector #4757 (where I mentioned this idea).

[brantkings]

oooh your feature would fix it for me!

[Mickeon]

Scene previews should be improved in the first place since their current implementation renders them... essentially useless.

• See Improve scene thumbnails #7232