Simplify data-structure used in "inline-diff"
Simplify data-structure used in "inline-diff"

*For each* HunkReference stored globally in `diff_view_hunks` we
compute a ReplaceLineInfo used internally.  Both essentially have the
same info, namely `section_start`, `section_start`, `line_types`, and
`line_contents` (named: `lines` in HunkReference) have the same value.
HunkReference additionally holds the back ref to the `hunk`.

We thus remove usage of the ad-hoc tuple `replaced_lines`, and just
pass and reuse `hunks` as stored in `diff_view_hunks`

divmain/GitSavvy,divmain/GitSavvy,divmain/GitSavvy