Fix LibreOffice braille scrolling (#19204)
Fixes #19152
Fixup for #18348,
Supersedes #19203, #19171
Summary of the issue:
In LibreOffice, it is not possible to use braille panning since #18348.
Description of user facing changes:
Panning works again in LibreOffice
Description of developer facing changes:
removed OffsetsTextInfo.allowMoveToOffsetPastEnd.
Description of development approach:
Rather than having one allowMoveToOffsetPastEnd class attribute, introduce a allowMoveToUnitOffsetPastEnd method that takes a unit.
