Support external diff algorithms in internal diff editor

[myfairsyer]

While #15661 asks for the ability to launch external diff programs in their own user interface I'd rather like VSCode to parse the patch formatted output of another (probably mainly cli?) diff tool and show the results in the regular built-in diff editor

In #15661 @joaomoreno suggested writing an extension but I suppose this here would not be possible with an extension, right?

Just like in #15661 one of the use cases I have in mind is using git's built in diff algorithms. For that use case I'd also love to see an option that respects what is being set in git's settings (although I guess this should be possible to be managed in an extension when the base functionality of using external diff algorithms in the internal diff editor is implemented, right?)

[alexdima]

Since last year, we have enhanced our diff algorithm with git's whitespace heuristic that brings diff hunks together (reduces their count in many cases) and have added another heuristic for comparisons when ignore trim whitespace is off. I think we should focus on doing additional improvements in our diff algorithm rather than integrating an external diff tool that at the end of the day also contains a diff algorithm...

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