TST: simplify cartopy integration testing (using cartopy 0.22)

[neutrinoceros]

Cartopy 0.22 was just released and is supposed to resolve a couple workarounds we've been using to test it.
Most notably, this version doesn't depend on GEOS, and as such, it can afford to have wheels, which should allow us to properly test it on all platforms for cheap !

[chrishavlin]

The ci_install.sh script was still installing geos -- which we shouldn't have to do anymore. I left comments pointing out those spots as well as a couple other further simplifications that I think are possible.

Also, adding cartopy>=0.22 as a proper dependency in yt[full] would further simplify the setup here. Thoughts on that?

[neutrinoceros]

The ci_install.sh script was still installing geos -- which we shouldn't have to do anymore. I left comments pointing out those spots as well as a couple other further simplifications that I think are possible.

yes, that is also what I assumed at first but unfortunately geos is still needed to build shapely (which is still a direct dependency to cartopy).

Also, adding cartopy>=0.22 as a proper dependency in yt[full] would further simplify the setup here. Thoughts on that?

this was also one of my goals for this PR but given how shapely is still a pain to install (the source distribution from PyPI doesn't build on Windows), I renounced that goal too;

[chrishavlin]

Oh huh, that's a shame... I think all my comments can be disregarded in that case.

[neutrinoceros]

I checked, and I think the title of this PR says it all

[chrishavlin]

Looking more carefully at shapely -- they do package geos. Did you try removing the geos install from the Ubuntu and Mac branch of the install script?

[chrishavlin]

I checked, and I think the title of this PR says it all

But the shapely docs make it pretty clear that you should only need to install geos explicitly if you want a specific version https://shapely.readthedocs.io/en/latest/installation.html maybe that's not the case in practice

[neutrinoceros]

ah ! Let's try not to build shapely from source then: it doesn't seem to be recommended any more by cartopy, and I assume it would save us installing geos too

[neutrinoceros]

Looks like it worked ! thank you for spotting this Chris, I will iterate a little more and then reopen for review

[neutrinoceros]

Note that wheels are only available for Python 3.9 and above. I don't think this is blocking here, but that's a sign that supporting Python 3.8 is becoming harder for us.

[neutrinoceros]

Another note: I think this works makes conda useless in CI (only used on Windows), but I'd prefer to defer dropping it to a follow-up PR.

[chrishavlin]

Nice! And removing conda if possible in a later pr makes sense to me.