Snapshot-based devtools (1st iteration)

[Thisen]

See #388.

• Impl
• Tests

This is the first iteration of snapshot-based devtools. It's not ready yet for public use.

[Thisen]

Everyone feel free to take a look.

@dai-shi with this current logic in Provider.ts:

if (
    typeof process === 'object' &&
    process.env.NODE_ENV !== 'production' &&
    process.env.NODE_ENV !== 'test'
)

How do I create tests for the devtools stuff? I could find a simple solution with NODE_ENV, but lets aim for a good way to run these tests.

CC: @Thiesl137

[dai-shi]

Great work. So far, so good. I'd like to spend time to think about better internal apis for second iteration.
For this iteration, remainings are 1) TODO to create final snapshot map, 2) tests?

process.env.NODE_ENV !== 'test'

This is something we are not happy with. I just added to pass some of tests (optimizations?), but happy to remove it and handle it in tests, if there's a solution (there must be).

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[Thisen]

@dai-shi Feel free to review now. Make sure to look at imports aswell, not sure how to deal with those without exposing a bunch of internal APIs.

I think we should let me be undocumented, while we iterate on this API.

[dai-shi]

Overall, it looks good to me for the 1st iteration.

[dai-shi]

#446 is merged. Please adjust this PR a bit.