Taskcluster updates

[bendk]

There are a couple updates that I'd like to make to our taskcluster code:

• Combine all these ENV setting statements into 1 line. That way we aren't creating so many docker layers.
• Switch away from our slightly weird rsync usage to copy fetched files (one of many examples). I think the reason we use rsync is to merge the fetched files with any existing files. For example, I just added an artifact that contains the files to add to the .m2 directory, but there may be other files already there. To fix this, I think we just need to update our code to not extract the tarballs into the fetches directory, and instead we can extract them directly into the directory we want to install to. I think the way to avoid extracting the tarballs is to use the longer-form schema for fetches (specified here)

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