Plugins API: Fix the plugin 'render' property validation

[sdnunca]

What?

PR fixes the plugin's render property validation which is failing for memoized components.

Why?

#78674 updated withSelect to return a memoized component. Plugins using withSelect in the render property now fail the typeof === 'function' validation.

We've previously made similar changes for the blocks API.

How?

Use the isValidElementType from the official react-is library to check the edit property's validity correctly.

Testing Instructions

1. Add memo (or use withSelect) to a plugin's render property.
2. Open the post editor.
3. Confirm you see the 'The "render" property must be specified and must be a valid function.' on trunk.
4. Confirm there's no error on this branch.

Testing Instructions for Keyboard

Screenshots or screencast

Before	After

Use of AI Tools

[github-actions]

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Co-authored-by: sdnunca <[email protected]>
Co-authored-by: Mamaduka <[email protected]>

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[github-actions]

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[Mamaduka]

Thank you, @sdnunca!

Do you mind adding a test case that would fail without this fix? I think checking that the memoize function component can pass the check is what we want to test.

[sdnunca]

Thank you, @sdnunca!

Do you mind adding a test case that would fail without this fix? I think checking that the memoize function component can pass the check is what we want to test.

Thank you for the feedback @Mamaduka.
I've added a separate test so we cover both the Component and memo cases.

[Mamaduka]

Thanks, @sdnunca!

The fix works as expected ✅