Teach add_test_(python|tcl) to parse explicit NO_DATA, NO_RT, NO_VALID,
and NO_OUTPUT keyword options for tests that do not need VTK_DATA_ROOT
or do not use a valid baseline image.  Factor add_test_python1 into
add_test_python and distinguish them with the NO_RT keyword argument.
Update call sites to produce identical test command lines before and
after this change.

Change-Id: I09f874b26aab409e55e7aa6f92412314540dbb85