refactor: remove unnecessary interface exports

- Remove export from IHighlight and IMultiHighlight interfaces
- Remove export from ISelectedDecoration interface
- Remove export from ISearchPosition interface
- Keep ISearchResult exported as it's used across multiple files
- Make ISelectedDecoration extend IDisposable for consistency

addons/addon-search/src/SearchEngine.ts

@@ -10,7 +10,7 @@ import type { SearchLineCache } from './SearchLineCache';
 /**
  * Represents the position to start a search from.
  */
-export interface ISearchPosition {
+interface ISearchPosition {
   startCol: number;
   startRow: number;
 }