Feature request: Change default library path on Windows

So I would say that I still believe Microsoft doesn't give clear
guidance for this.

Sure, there is some ambiguity on where MS would prefer these kinds of
files. But what is clear is that the current location USER/Documents
is causing a serious issue.

And while we can all understand frustration with Microsoft, Windows
users represent a major proportion of the R install base. So let's see
what we can do to help out those users. Changing the default location
to either USER/R or USER/AppData/Local/R would help a lot of users,
both beginners and those with moderate experience who switch to a new
cloud backup.

Microsoft is unlikely to put out new guidance any time soon. And the
current guidance doesn't seem opposed to putting R libraries in either
suggested location. So how about we just pick one (I suggest USER/R
for simplicity) and discuss how to go about making the change?

-Steve