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
- [ ] Component: `ClipboardButton`
- [ ] Component: `ColorSettings`
- [ ] Component: `ContentPicker`
- [ ] Component: `ContentSearch`
- [ ] Component: `CustomBlockAppender`
- [ ] Component: `IconPicker`
- [ ] Component: `Image`
- [ ] Component: `Link`
- [ ] Component: `IsAdmin`
- [ ] Component: `MediaToolbar`
- [ ] Component: `Optional`
- [ ] Component: `Repeater`
- [ ] Component: `RichTextCharacterLimit`
- [ ] Component: `PostAuthor`
- [ ] Component: `PostTermList`
- [ ] Component: `PostDate`
- [ ] Component: `PostExcerpt`
- [ ] Component: `PostFeaturedImage`
- [ ] Component: `PostPrimaryTerm`
- [ ] Component: `PostTitle`
- [ ] Component: `PostMeta`
- [ ] Hook: `useAllTerms`
- [ ] Hook: `useTaxonomy`
- [ ] Hook: `useIsSupportedTaxonomy`
- [ ] Hook: `usePost`
- [ ] Hook: `usePrimaryTerm`
- [ ] Hook: `useSelectedTermID`
- [ ] Hook: `useSelectedTerms`
- [ ] Hook: `useSelectedTermsOfSavedPost`
- [ ] Hook: `usePostMetaValue`
- [ ] Hook: `useFilteredList`
- [ ] Hook: `useHasSelectedInnerBlock`
- [ ] Hook: `useIcons`
- [ ] Hook: `useMedia`
- [ ] Hook: `useRequest`
- [ ] Hook: `useBlockParentAttributes`
- [ ] Hook: `useScript`
- [ ] Hook: `useIsPluginActive`
- [ ] Hook: `usePopover`