ci: use with-connect action for Posit Connect integration tests

[nealrichardson]

This PR uses https://github.com/posit-dev/with-connect to modernize the Posit Connect test suite and get running again. See a passing CI run here: https://github.com/rstudio/pins-python/actions/runs/19110527979/job/54606158812?pr=351#step:5:192

Other changes include:

• Use CONNECT_SERVER and CONNECT_API_KEY env vars for those values by default, for consistency with other Connect API clients and the Connect documentation
• Rebrands _HackyConnect to LoginConnectApi because all it does is allow you to log in with username and password instead of API key. But left the old _HackyConnect in there because I found at least one other of our packages using it. Will circle back to remove it once that's cleaned up.
• One test, test_board_pin_search_admin_user, is skipped: for some reason this didn't work with the new setup. However, I think it is really just testing how Connect does authorization, not how pins works, so I'm not sure it is necessary.

There's more cleanup I'd like to do here, but maybe I'll follow up with something else, just to keep this PR more focused.

Fix #341

[isabelizimm]

Is there a way to set up with-connect locally we can add in the Makefile? like with-connect -- xyz, even if it makes assumptions about having a .lic file in a certain location or other creds.

[nealrichardson]

I added a note to CONTRIBUTING.md about how to install and run locally--is that enough or would you like a make target too? Easy enough to add one.

[nealrichardson]

On second thought I'll just do this, there is still a bit of fussing that the GHA job does to get it working right, so it would be nice to encapsulate that for local testing.

[isabelizimm]

Yeah, there's just enough complexity in setup that having a make target would be very helpful. Thanks!

[nealrichardson]

Added in 3dc96dd

[isabelizimm]

Nice! Was able to run everything locally, the dev experience is super easy. Thanks for updating this!