Manual cherry-pick Tools/PyUtils/bin/lstags master changes into 21.0
This MR manually cherry-picks !22622 (merged) into 21.0. With this change, lstags
will read the packages.txt
from the $WorkDir_DIR
to list the locally built packages. It also cleans-up any reference to CMT/SVN
-era stuff.
This MR is relevant to the discussion in ATLASJT-399.
cc: @mavogel