(populate) - refactor and increase reliability of query-reading

[yankovalera]

Summary

(relates to #964) Increase feature-set of the populateExchange. Address "classic" mode. As discussed with @JoviDeCroock we might address other cases in other PRs.

"Classic" mode for populate exchange:

mutation { addTodo @populate }

We find out what type is used inside of the [[Mutation]] and look in our data-structure what fields we've used for this type.

Set of changes

[changeset-bot[bot]]

🦋 Changeset detected

Latest commit: b6c5240f673c5f911354accbf48c5744224b1da1

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 1 package

Name	Type
@urql/exchange-populate	Patch

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[kitten]

Superseded by #2897. Co-Author tag should potentially be added there