Upgrade to testthat 3e

[MichaelChirico]

trafficstars

I was aiming to send along a PR dropping the {mockery} dependency but it's a bit of a bigger project than at first glance despite the small footprint of {mockery}:

https://github.com/r-lib/cpp11/blob/dc93fb84f482c2ac93b5578fee955c75a40b093f/tests/testthat/test-utils.R#L28 https://github.com/r-lib/cpp11/blob/dc93fb84f482c2ac93b5578fee955c75a40b093f/tests/testthat/test-vendor.R#L4

Because currently {cpp11} uses a lot of describe(..., it(...)) style tests that require more lift to move to 3e.

Filing this issue as an earmark that it would be something nice to have.

[pachadotdev]

I implemented multiple changes that include this request here: https://github.com/r-lib/cpp11/pull/405

[pachadotdev]

hi @DavisVaughan I wanted to follow up on this. I hope this PR is useful. https://github.com/r-lib/cpp11/pull/405