Kiota should warn the user when re-generating that all changes did manually by them will be overridden

[maisarissi]

Sometimes users find points of improvements in the Kiota generated files, for both client and plugin generation.
For example, Kiota might have an issue in the deserialization logic, and the user decided to fix it manually in the generated code. Or when creating a plugin, the user might update the generated plugin to add more conversation starters, or enhance the function descriptions so Copilot can be accurate when matching the functions.

When editing an existing plugin/client in the VS Code extension, and regenerating or when clicking on "re-generate" codelense in the manifest.json, the user should get an warn message saying all changes made manually to the generated files will be overriden.

Acceptance Criteria:
1 - When editing an existing client, when clicking on "Re-generate" button , Kiota should warn the user all manual changes will be overridden.
2 - When using the codelense in the workspace.json file , the user should also get the warning.
3 - The warning should be shown every time the user hits "Re-generate", both in the API Explorer button or in the codelense.
4 - The regeneration should only be done when the user hits on "Yes, override it".
5 - When the user hits on "Cancel" after getting the warning, Kiota shouldn't re-generate the client/plugin.