Problem

It would be useful to be able to share a single cycler instance across multiple axes, so that plotting on one axes advances the same instance on all of them.

Proposed Solution

cycler = <some cycler instance>
ax1.set_prop_cycle(cycler)
ax2.set_prop_cycle(cycler)

should use the same cycler instance. Alternatively, if this is deemed unacceptable due to backcompat breakage (even though I believe this can get a proper deprecation warning), one should at least be able to do e.g.

cycler = <some cycler instance>
it = iter(cycler)  # or it = cycler.iter(), or whatnot
ax1.set_prop_cycle(it)
ax2.set_prop_cycle(it)

which has no backcompat concerns as set_prop_cycle(single_arg) currently requires single_arg to be exactly a Cycler instance.

Additional context and prior art