[Premake] Removed unused/unnecessary subprojects.

- Testing currently doesn't work
- VFS Dump is unused. You can use internal function for it
- Demos are only for fun
- Trace Dump & Trace Viewer (unsure, but ok)

You can re-enable them by changing values: enableTests and enableMiscSubprojects in main premake file.

In the future there should be xb command support to overwrite them

src/xenia/base/premake5.lua

@@ -17,4 +17,6 @@ project("xenia-base")
     "debug_visualizers.natvis",
   })
 
-include("testing")
+if enableTests then
+  include("testing")
+end