Adds the groundwork needed in order to persist multi-line suggestions,
while providing the parsing strategy which will be reused for the
**Preview** as well.
This is an issue that can only be seen through EE. Further
details can be seen on
https://gitlab.com/gitlab-org/gitlab-ee/issues/9876. In general
we should always use the latest diff version of a file in order
to both create and apply suggestions.
1. Avoid suggestions being applied on the same file
from reverting previous changes
2. Gracefully use and handle file changes error
when updating the file (though, it does not totally
solves the sync problem for multiple suggestion
applications at once)
