Backspace should not delete the whole cluster #19582
Description
Describe the bug
When characters form a cluster, backspace deletes the whole cluster. This is undesirable, since fixing a typo at the last character requires user to type the whole cluster again. Moreover, as Windows only removes the last character on backspace, Windows users used to this behavior end up accidentally deleting a lot of text.
To Reproduce
Backspacing e.g. किः will delete everything, or கா with the last character repeated (GitHub does not like it and removes it)
Expected behavior
remove just the last character
Avalonia version
12.0.999+27859b9e5456bc5a1ea4146ec8d958c66255b1e0
OS
Windows
Additional context
Note that the current behavior is not unattested (e.g. Teams using Harfbuzz). Emoji and VS might have special behavior.