fix: decycle potentially cyclic structures before serializing

[sarahdayan]

This introduces a decycle utility to replace cyclic references in objects before serializing them with JSON.stringify.

It uses a slightly modified version of Crockford's cycle.js, which MDN recommends. This works better than JSON.stringify's replacer, because the latter walks every node in the object, making it difficult to preserve non-circular structures like the following:

const a = { a: 1 };
const obj = [a, a]; // JSON.strinigfy can handle this, we don't want to end up with `[{ "a": 1 }, "[Circular]"]`

Whenever a circular reference is met, it's replaced with [Circular] (à la Jest).

{
  "self": "[Circular]"
}

If sources contain complex objects (e.g., VNodes with SVGs), decycling could have a negative impact on performance. I've therefore introduced a change to invariant, making it accept message in the form of a function to execute only when the condition isn't met.

fixes #618

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friendly-lamarr-y7tur	Issue #618

[francoischalifour]

Nice change–we could definitely reuse these dev warnings in our other frontend libraries (and abstract them more).

[sarahdayan]

we could definitely reuse these dev warnings in our other frontend libraries (and abstract them more)

I've added a ticket for this in the backlog. It could be an onboarding task if we don't get to do it before.