Fix issue in RTE with image resize

If you upload an image in PTE and resize it in RTE, the image
was lost. This commit fixes it.


- Introduce getSourceMapAttributes function for centralized attribute management
- Update image and playable extensions to use new source map attributes
- Refactor sourcemap extension to use centralized attribute function
- Modify image serialization logic to handle different source tag names
- Add drag functionality for element manipulation in tests
- Implement image resizing test in content editor

Changelog: fixed