Early in 2.0, we began caching the raw insert/delete counts from the

patch file on FileDiffData. We didn't compute the displayed

insert/delete/replace counts because they couldn't be computed at will

without going through a diff generation cycle. They're also more

display-specific, as they depend on the particular diff renderer used,

so they're not a good fit for FileDiffData.
The values we were storing were also a bit expensive to get, since we

had to fetch a DiffFileData for each one. That meant that on the

dashboard, adding the Diff Size column would end up doing 1 query per

row.
Those counts are useful, even if we can't always rely on having them.

We also want all counts closer to avoid the fetches. This change

calculates them at render time and stores them on the FileDiff's

extra_data.
In particular, the following are now stored:

raw_insert_count
raw_delete_count
insert_count
delete_count
replace_count
equal_count
total_line_count

In the new terminology, the insert/delete counts are for the processed

(rendered) counts, while the raw versions are from the patch.
FileDiff's set_line_counts has been updated to take all those line

counts. Each are optional.
There's also now a get_line_counts that returns all the counts that are

available, and a DiffSet.get_total_line_counts that computes the counts

for all files. For these, there's a guarantee that insert_count,

delete_count, raw_insert_count, and raw_delete_count will be returned.

The rest depend on whether they've been set before.
If the diff hasn't been rendered yet, the non-raw insert/delete counts

will be set to the raw versions. This helps ensure we have at least

something. Callers using those will get the processed versions after

the first render.

Unit tests pass.
Checked the counts after the first call to get_line_counts (without

re-rendering the diff) and saw that only the raw/non-raw insert/delete

counts were there, and that they were the same value.
Rendered a diff and checked again. Saw all the other counts filled in,

and saw that the non-raw insert/delete counts were no longer matching

the raw ones.
Added the Diff Size column to my datagrid and saw those counts.
Checked the codebase for any and all references to the old properties

that were removed. Didn't see any left.