[DISCUSS] Release Apache Daffodil 3.9.0

[Steve Lawrence]

In keeping up with an approximately 3 month release cycle, I'd like to start a 
discussion about releasing Daffodil 3.9.0. We've merged a few changes to improve 
performance a handful of bug fixes, and we have a number of open PR's for bug 
fixes and dependency updates that are close to being merged. Are there any other 
changes needed for 3.9.0?

If not, once the non-WIP PRs are merged, I'll volunteer to be the release 
manager, hoping to start the process on Thurs Sept 19.

- Steve