[perl #43333] [TODO] config/auto/cpu.pm: Write unit tests

[James Keenan via RT]

Configuration step classes gen::cpu and auto::cpu were merged, given the
name auto::cpu (because it's an automatic probe and does not generate
files) and given the place in the configuration step sequence formerly
held by gen::cpy.  Tests were added.  The code which remains uncovered
by tests is mostly eval of hints files -- and this is going to prove
unreasonably difficult to test.  So I'm closing the ticket.