Present a bit more information about the differences between pipelines

[paul-butcher]

diff_tool presents a pass/fail/warning view of the differences between two versions of the API. However, when the differences are significant, we are left with a "Well, what now?" feeling. In #2549, there were 2400 missing records, but no simple way to get a sample of what is missing.

Similarly, when the differences are insignificant (e.g. there are two Botany records that occasionally swap places in the search results or there are less than 10 [missing|extra] documents), that still takes a degree of investigation. One has to open a browser tab for each API, copy the path onto each and eyeball them. This information then vanishes like tears in the rain, and is not associated with the deployment build.

It would be nice to have some more data presented either as part of diff tool, or at least for there to be a more convenient way to discover it.

See also: #2550