Contributes to https://gitlab.com/gitlab-org/gitlab/-/issues/16950

Follow-up for
https://gitlab.com/gitlab-org/gitlab/-/merge_requests/55105

Extend to Gitlab::WordDiff::ChunkCollection class to generate
`marker_ranges` based on chunks received from `git diff
--word-diff=porcelain` output.

Each chunk can be an unchanged string (starts with ` `), new
string (starts with `+`) or removed string (starts with `-`).

While parsing we collect chunks until we receive a newline
delimiter. Then we are combining them together to generate
Gitlab::Diff::Line object and assign MarkerRanges for changed parts of
the diff line.