Make `assertrepr_compare` public.

[brunns]

The assertrepr_compare function, in _pytest.assertion.util, could be very useful in contexts outsides pytest's assertions. Might you consider exposing it as part of pytests public API so other packages can make use of it?

[Zac-HD]

Very unlikely sorry, as the details are tied to lots of pytest internals and we would then have to maintain it.

Instead, I suggest that interested projects copy-paste out the relevant code, which is after all under an MIT license!

[brunns]

OK, thanks!