Complete overhaul of the Legion package to better capture a more
up-to-date set of configuration options and variants. This update
adds additional flexibility and features that were requested by
users.
* Add version 21.03.0 and "stable" branch
* Remove all older numeric versions
* Add support for CUDA, Python, PAPI support and more
* Add maintainer
* This no longer uses the Spack `gasnet` package: it defaults to
using an embedded gasnet or can be pointed to an external
24c87e07b5