FilePicker and Markdown: Remove file entries on destroy and file change event

[stsrki]

Further improves on #5980

I have changed how removeFileEntry is called. Now, it removes all entries when the component is destroyed and when the file(s) is changed. If there were previous file entries, then it will remove them.

I have also deleted RemoveFileEntry as it didn't make sense to keep it.

[tesar-tech]

I agree with "batch removal", but I liked the call from dotnet more - because there we can tell when we want that (after OnImageUploadChanged)
If you do it in js you basically moving the logic there, which gets confusing and hard to maintain. imo the js calls should be as stupid as possible - while keeping the decisions/flows/logic in c#.

[stsrki]

I agree with "batch removal", but I liked the call from dotnet more - because there we can tell when we want that (after OnImageUploadChanged) If you do it in js you basically moving the logic there, which gets confusing and hard to maintain. imo the js calls should be as stupid as possible - while keeping the decisions/flows/logic in c#.

The problem with fully JS or fully C# side is that none works 100% times. It all depends on the specific implementation. So I think we can have a hybrid. Use JS fully for FilePicker, and hybrid for Markdown.