refresh: Refactor option handling and '--recursive'.

refresh: Refactor option handling and '--recursive'.

This allows us to combine '--recursive' with other options (-u, -m,
etc.), turns off warnings when '--recursive' is used, and avoids the
hazards of I/O in the presence of multithreading.

* guix/scripts/refresh.scm (options->packages): New procedure, with code
formerly in 'guix-refresh'.
(refresh-recursive): Remove.
(guix-refresh)[keep-newest, core-package?, args-packages, packages]:
Remove.
[warn?]: Set to #f when RECURSIVE? is true.
Call 'options->packages' in monadic context.