Yet another retraction test

Simple retraction test with two cylinders and two cones.

The cylinders are useful for testing combing / wiping / coasting settings.
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Those settings have less impact on the cones as they narrow.

This means the cones are more difficult to print cleanly and are useful for fine tuning for finer detail prints where combing / wiping / coasting doesn't help as much.

The narrow taper on the cones also makes this a good test of hotend cooling, as the fine points will melt and fall apart if cooling is poor.

Print using the settings you'll be printing in - it's tempting to speed up by increasing layer height, but the layer height can affect stringing.