Test: Add tests to @cloudflate/unenv-preset

[vicb]

The unenv preset was added to the repo recently.

We need to add tests to the package

As a first step, we can add test to fixtures/nodejs_hybrid_app but we will need to move those tests to @cloudflate/unenv-preset so that we can use:

• The most recent workerd by setting MINIFLARE_WORKERD_PATH to the workerd from @cloudflate/unenv-preset
• The dev version of the preset by setting WRANGLER_UNENV_RESOLVE_PATHS to the dev version of the preset

Note from Pete: There is some overlap with the existing tests. We should remove the overlap. Ideally we should run the tests both with the fixtures and the unenv preset updates - this will require to check the workerd version and skip tests requiring a newer workerd that is available when running the fixture tests (unenv-preset might use a newer workerd version than wrangler).