BuildSystem: Cleanup userspace directory layout

userspace programs are now in userspace/programs
userspace tests are now in userspace/tests

This makes listing userspace projects much cleaner. Libraries were
already separated to their own directory, so other programs should also.

userspace/tests/test-mouse/CMakeLists.txt

@@ -0,0 +1,10 @@
+set(SOURCES
+	main.cpp
+)
+
+add_executable(test-mouse ${SOURCES})
+banan_include_headers(test-mouse ban)
+banan_include_headers(test-mouse libinput)
+banan_link_library(test-mouse libc)
+
+install(TARGETS test-mouse OPTIONAL)