[testing/bdd] async describe

[teidesu]

Is your feature request related to a problem? Please describe.

in vitest we can use async functions as a callback to describe(), which allows setting up group-related resource, e.g.:

describe('foo', async () => {
  const foo = await createFoo()
  afterAll(() => foo.destroy())
  
  // ... tests ...
})

however describe currently doesn't allow async functions to be passed

Describe the solution you'd like

support async describe callbacks

Describe alternatives you've considered

• move all awaits to top level - the downside is that group-related stuff stops being grouped
• initialize everything with a beforeAll hook - the downside is that we have to use non-null assertions for typescript + increases boilerplate