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Cache File: use panels to organize UI

This adds interface panels to organize the Cache File UI parameters for
modifiers and constraints into related components: velocity, time, and
render procedural.

Properties relating to the three aforementioned components are separated
from `uiTemplateCacheFile` into their own functions (e.g.
`uiTemplateCacheFileVelocity` for the velocity one), which are in turn
called from the specific panel creation routines of the modifiers and
constraints (for constraints, the functions are exposed to the RNA).

`uiTemplateCacheFile` now only shows the properties for the file path,
and in the case of constraints, the scale property.

The properties that are only defined per modifier (like the velocity
scale), are shown in the proper modifier layout panel if applicable.

Reviewed By: sybren

Differential Revision: https://developer.blender.org/D13652