Use Diff Match Patch by default when available (#12485)
Diff Match Patch (DMP) was included but disabled by default in 2021.1. It fixes #3200 and allows for drastically fewer cross-process calls in UIA console, improving performance in busy applications.
This PR enables DMP by default to allow for wider user testing in master snapshots. If user feedback is positive, use by default in 2021.2.
