Prefer Difflib in scrolling LiveText objects (#12974)
In LiveText objects that are constrained to onscreen text (i.e. where text scrolls off the screen), DMP is sometimes unable to correctly calculate new text, leading to choppy and inconsistent new text reporting.
Description of how this pull request fixes the issue:
Prefer Difflib in pre-FORMATTED UIA console (including legacy mode) and DisplayModelLiveText objects. Users can override this choice in advanced settings for testing or if DMP really provides a supperior experience in their situation.
