test: namespace cleanup, common -> src, tenv -> lib, etc.

Signed-off-by: Joachim Wiberg <troglobit@gmail.com>

TODO.org

@@ -1,6 +1 @@
-* DONE fix pid parser, //run/foo.pid -> /var/run///run/foo.pid
-** DONE test framework refactor 'texec sh -c ...' -> 'run ...'
-* TODO Clean up tests a bit
-* TODO Drop tenv or common and rename sysroot
-* TODO rename test/lib.sh to start.sh or sth