Consider running `Hypothesis` tests with `-We`

Currently we never run tests in CI with -We.

» ag '\-W(e| error)' .github
.github/workflows/build.yml
79:        run: autoreconf -ivf -Werror
                        

This might be a problem for several reasons:

• Warnings might be raised and unseen for quite some time
• -We can break something that it should not break, we never check for it

This is especially true for Hypothesis runs, which has its own warnings, sometimes not very expected ones, like in https://github.com/python/cpython/pull/136384

My proposal: let's try to research if it is possible and if it is a good idea. And maybe eventually run Hypothesis tests with -We in our CI.

Please, share your ideas / concerns about this change.