Adds a new `Effect` type which for now just points to the `SimpleEffect` type, in prepartion for later in the stack where we add more. --- [//]: # (BEGIN SAPLING FOOTER) Stack created with [Sapling](https://sapling-scm.com). Best reviewed with [ReviewStack](https://reviewstack.dev/facebook/react/pull/31557). * #31523 * __->__ #31557 * #31556 * #31555 DiffTrain build for [053b3cb050](https://github.com/facebook/react/commit/053b3cb0503e26da6d1dfa02b74fa52e30936bd6)
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