refactor(core): re-implement useAtom with useReducer

[dai-shi]

uMS won't land, #686 doesn't work so far.
I feel like simpler solution with useReducer would work better.
This simplifies a lot. Also, fixes weird issues in devtools.

[vercel]

This pull request is being automatically deployed with Vercel (learn more).
To see the status of your deployment, click below or on the icon next to each commit.

🔍 Inspect: https://vercel.com/pmndrs/jotai/9Zch3BP9tA21Q54SQWYs4oCEXuEL
✅ Preview: https://jotai-git-barely-use-reducer-pmndrs.vercel.app

[dai-shi]

This improves https://github.com/dai-shi/will-this-react-global-state-work-in-concurrent-rendering results:

v1.3.2

  jotai
    with useTransition
      ✓ test 1: updated properly with transition (3562 ms)
      ✓ test 2: no tearing with transition (122 ms)
      ✓ test 3: ability to interrupt render
      ✕ test 4: proper branching with transition (7543 ms)
    with intensive auto increment
      ✕ test 5: updated properly with auto increment (13214 ms)
      ✕ test 6: no tearing with auto increment (4 ms)

33a40b0

  jotai
    with useTransition
      ✓ test 1: updated properly with transition (3555 ms)
      ✓ test 2: no tearing with transition (119 ms)
      ✓ test 3: ability to interrupt render (1 ms)
      ✕ test 4: proper branching with transition (8503 ms)
    with intensive auto increment
      ✓ test 5: updated properly with auto increment (3233 ms)
      ✕ test 6: no tearing with auto increment (2 ms)

[dai-shi]

I would like to test if react devtools work before merging. (codesandbox ci is not working. 😓 )

[codesandbox-ci]

This pull request is automatically built and testable in CodeSandbox.

To see build info of the built libraries, click here or the icon next to each commit SHA.

Latest deployment of this branch, based on commit 2e96c2c:

Sandbox	Source
React	Configuration
React Typescript	Configuration
React Browserify	Configuration
React Snowpack	Configuration
Next.js	Configuration

[Thisen]

Looks good to me. Surprised that it didn't require test changes.