GH-86275: Implementation of hypothesis stubs for property-based tests, with zoneinfo tests (#22863)

These are stubs to be used for adding hypothesis (https://hypothesis.readthedocs.io/en/latest/) tests to the standard library.

When the tests are run in an environment where `hypothesis` and its various dependencies are not installed, the stubs will turn any tests with examples into simple parameterized tests and any tests without examples are skipped.

It also adds hypothesis tests for the `zoneinfo` module, and a Github Actions workflow to run the hypothesis tests as a non-required CI job.

The full hypothesis interface is not stubbed out — missing stubs can be added as necessary.

Co-authored-by: Zac Hatfield-Dodds <zac.hatfield.dodds@gmail.com>