dotnet-fsi doesn't allow the use of up-arrow or moving the cursor without --readline

[cartermp]

1. Install a build of .NET Core that comes with dotnet fsi (link)
2. Launch it
3. Attempt to move the cursor around

This fails with dotnet fsi. However, it works fine with fsharpi from Mono:

[zpodlovics]

@cartermp Please also try the dotnet fsi with --readline+

#2407 (comment)

[cartermp]

Thanks @zpodlovics this actually solves this problem and #6185, and lets ctrl+D work if you hit it twice (#6188).

[sasmithjr]

--readline+ also fixes an issue where the up arrow on macOS seems to be broken.