Fix bottom panel pinning

[KoBeWi]

Fixes #113438

[lodetrick]

I was thinking about this earlier, and since bottom panels can be moved to other docks I wonder if the pin should be a global feature. The pin solved the problem of clicking on nodes or resources would focus new docks when you wanted to keep one specific dock open (like the animation dock when keying properties). This worked when transient docks were confined to the bottom panel. But now that transient docks can be in different places, for example the tilemap dock could obscure the inspector if they were in the same slot (which I do personally).

A potential solution might be to just prevent focusing from code if the lock button is pressed, in which case the button might be better next to the distraction free button. I'm curious what you think

[akien-mga]

Thanks!