refactor!: remove TeraEd facade (MovingBlocks#5115)

* git rm -r facades/TeraEd
* remove remaining references to TeraEd

TeraEd is a facade wrapping the game itself into a desktop application to provide additional tools "around" it.
For instance, it was used to tweak shader parameters while the game was running.
Ideas for extension of this facade included monitoring capabilities, for instance, inspecting the state of the ECS, but were never implemented.

The benefit of having this outer layer is that we could augment the game itself with additional developer information without baking those into the game itself.

TeraEd used Swing and AWT for its UI.

The TeraEd facade was unused for a long time and has fallen victim to bit rot.
The logic handling state changes to shader parameters was commented out 6 years ago in b10b0f6.

.gitignore

@@ -16,7 +16,6 @@
 extensions
 /facades/*
 !/facades/PC
-!/facades/TeraEd
 !/facades/subprojects.gradle
 /modules/*
 !/modules/subprojects.gradle

config/groovy/facade.groovy

@@ -1,7 +1,7 @@
 
 class facade {
 
-    def excludedItems = ["PC", "TeraEd"]
+    def excludedItems = ["PC"]
 
     def getGithubDefaultHome(Properties properties) {
         return properties.alternativeGithubHome ?: "MovingBlocks"