Audit: Ensure all components & hooks function as intended for any user role

[fabiankaegy]

We have identified that some components are creating unexpected results for users with lower privileges such as author. Therefore we should perform an audit and ideally run tests for the components as different user roles to prevent issues like these in the future.

See #245

Tasks

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1. Component: ClipboardButton
2. Component: ColorSettings
3. Component: ContentPicker
4. Component: ContentSearch
5. Component: CustomBlockAppender
6. Component: IconPicker
7. Component: Image
8. Component: Link
9. Component: IsAdmin
10. Component: MediaToolbar
11. Component: Optional
12. Component: Repeater
13. Component: RichTextCharacterLimit
14. Component: PostAuthor
15. Component: PostTermList
16. Component: PostDate
17. Component: PostExcerpt
18. Component: PostFeaturedImage
19. Component: PostPrimaryTerm
20. Component: PostTitle
21. Component: PostMeta
22. Hook: useAllTerms
23. Hook: useTaxonomy
24. Hook: useIsSupportedTaxonomy
25. Hook: usePost
26. Hook: usePrimaryTerm
27. Hook: useSelectedTermID
28. Hook: useSelectedTerms
29. Hook: useSelectedTermsOfSavedPost
30. Hook: usePostMetaValue
31. Hook: useFilteredList
32. Hook: useHasSelectedInnerBlock
33. Hook: useIcons
34. Hook: useMedia
35. Hook: useRequest
36. Hook: useBlockParentAttributes
37. Hook: useScript
38. Hook: useIsPluginActive
39. Hook: usePopover