feat: Add RandomEffectController

[st-pasha]

Description

Add RandomEffectController -- a controller that makes the duration of some other effect controller random. This could be useful if the user wants to inject some amount of unpredictability into the effect.

Checklist

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Breaking Change

• No, this is not a breaking change.

[luanpotter]

I have a feeling this could be useful in a general context, not only to random effect controller;
For example, on Gravity I introduced a method similar to Uniform Random Variable
If so, we could move it to its own file and add factory methods to create both private implementations.
Thoughts?

[spydon]

Probably as a follow-up though?

[luanpotter]

LGTM