Support for modifying source in compare clipboard editor

[SougandhS]

For https://github.com/eclipse-platform/eclipse.platform/pull/1862#issuecomment-3028138890

follow-up to https://github.com/eclipse-platform/eclipse.platform/pull/1862

Supports modifying the source from compare editor itself

https://github.com/user-attachments/assets/2f1b60b2-8786-491c-adb1-e30e751009ee

[github-actions[bot]]

Test Results

 1 947 files  ±0   1 947 suites  ±0   1h 33m 49s ⏱️ - 3m 52s  4 720 tests ±0   4 696 ✅ ±0   24 💤 ±0  0 ❌ ±0  14 160 runs  ±0  13 993 ✅ ±0  167 💤 ±0  0 ❌ ±0 

Results for commit 443d921d. ± Comparison against base commit 401d4834.

:recycle: This comment has been updated with latest results.

[SougandhS]

One more thing I have to handle

[SougandhS]

https://github.com/user-attachments/assets/21b185b3-140b-4ceb-9699-72bfaaadcbc0

[SougandhS]

Hi @iloveeclipse, I have added the missing modify functionality 👍

[vogella]

@iloveeclipse I think you suggest that @SougandhS adds this. Can you review?