[Feature Request] An easy way to mock all Recoil state in bulk for testing/storybooking

[ashmind]

When building Storybooks of components that need Recoil state, it would be great to have an easy way to provide all state, including selectors. What I mean is something like this:

<TestRecoilRoot state={[
  [atom1, value1],
  [atom2, value2],
  [selector3, value3],
  [selector4, value4]
]}>
  <ComponentThatNeedsRecoil />
<TestRecoilRoot>

As mentioned in #1433 (comment) setting selectors directly raises invalidation and consistency concerns, however with a test-specific root I would not worry too much.

In fact the state here can be completely immutable, and any attempts to set an atom could go to an event instead, e.g:

<TestRecoilRoot state={[[atom1, value1]]} onSetState={({ state, value }) => { ... }}>
  <ComponentThatNeedsRecoil />
<TestRecoilRoot>

(which allows very straightforward spying on state updates)

Additionally, to cut down on boilerplate further, TestRecoilRoot should not share caches with any other roots, so manual approach like https://recoiljs.org/docs/guides/testing#clearing-all-selector-caches should no longer be required if using test root.