test: Assert useMediaUpload hook

[dcalhoun]

What?

Assert useMediaUpload hook functionality.

Why?

Improve stability.

How?

Add automated test file.

Testing Instructions

N/A, no user-facing changes.

Accessibility Testing Instructions

N/A, no user-facing changes.

Screenshots or screencast

N/A, no user-facing changes.

[Copilot]

Pull Request Overview

This PR introduces automated tests for the useMediaUpload hook to ensure its functionality regarding filter registration, unmount behavior, and interaction with the media library.

• Added a test file for the hook with multiple assertions covering filter registration and cleanup.
• Added a mock file for WordPress hooks to support testing.

Reviewed Changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
src/components/editor/test/use-media-upload.test.jsx	New test file asserting hook behavior including filter addition, removal, and media library interaction.
mocks/@wordpress/hooks.js	Provides mock implementations of addFilter and removeFilter for testing purposes.

Comments suppressed due to low confidence (1)

src/components/editor/test/use-media-upload.test.jsx:64

• [nitpick] Consider renaming 'FilterCallback' to a more descriptive name (e.g., 'MediaUploadComponent') to clarify its role in rendering the filter component.

let FilterCallback;

[adalpari]

LGTM!