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Animation: allow marking actions as cyclic for Cycle-Aware Keying.

When a manual frame range is set, allow marking an action as having
Cyclic Animation. This does not affect how the action is evaluated,
but the Cycle-Aware Keying option will automatically make any newly
added F-Curves cyclic. This allows using the option from the start
to build the cycle, rather than only for tweaking an existing loop.

The curves are made cyclic when they have only one key, either
after inserting the first key, or before adding the second one.
The latter case avoids the need to manually make the first added
curve cyclic after marking a newly added action cyclic.

Differential Revision: https://developer.blender.org/D11803