Add Partially Deobfuscated Classes panel

[NebelNidas]

Following up the discussion on Discord from May, I've split up the deobfuscation panel into two: A Partially Deobfuscated Classes panel and a Fully Deobfuscated Classes one.

While being at it, here are some related changes I made:

• Added a class counter to the individual panels
• Improved readability of the moveClassTree function, fixed a bug introduced over two years ago via QOL fixes - Volume 2 #239 which rendered the last else condition unreachable
• Made a common ClassPanel abstract class which the three other class panels inherit from. Also moved them into a new subpackage, although I wasn't quite sure how to name it, so please tell me if you have a better name
• Removed some duplicated code from GuiController.java, it now uses the methods from Gui.java
• Renamed DeobfPanelPopupMenu to ClassPanelContextMenu, as it can be used on all three panels now

It may not be the cleanest of implementations, but hey, it works 😄

[NebelNidas]

Works fine with my testing. The only issues left are ones that have to be fixed by other PRs:

• value and valueOf in Enums are currently reported as renamable, even though you can't actually rename them. This leads to 100% deobfuscated Enums to stay in the Partially Deobfuscated Classes panel. Would be fixed by Make enum methods values and valueOf unmappable #470.
• Anonymous classes, which obviously cannot be renamed, are currently undetectable, so classes containing these will also never move to the Fully Deobfuscated Classes panel. Detection for these depends on Fix mapping stats not skipping anonymous classes #469.
• There are a few issues introduced by the Nested Packages PR, namely Ghost entry after moving class to another package and back #471, renaming packages via the context menu on the class panels is broken and the "Collapse All" option doesn't work correctly anymore. These don't have to do anything with my PR.
• Having three class panels now amplifies this issue: Marking class as deobfuscated errors when other classes are already deobfuscated #483. It happens more often now, since classes move between panels more often.

[NebelNidas]

This PR has some serious performance problems when importing larger JARs, and to be fair, the UI isn't great either with how clamped up everything gets, I think this needs a larger overhaul later down the line when my new IR stuff is finished and Matcher support gets added.