[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/cpu/premake5.lua

@@ -21,9 +21,7 @@ project("xenia-cpu")
   local_platform_files("hir")
   local_platform_files("ppc")
 
-include("testing")
-include("ppc/testing")
---  filter({"configurations:Release", "platforms:Windows"})
---  buildoptions({
---    "/O1",
---  })
+if enableTests then
+  include("testing")
+  include("ppc/testing")
+end