refactor test for loading/emit changes and nextFetchPolicy

[phryneas]

This backports the big new test from #12556 so we can see what the changes in behaviour in the two braches are.

Look at commit 6c7d562 (#12620) here.

New behaviour on the left, old behaviour on the right.

[changeset-bot]

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Latest commit: 093fde8

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[pkg-pr-new]

npm i https://pkg.pr.new/@apollo/client@12620

commit: 1e3c06c

[github-actions]

size-limit report 📦

Path	Size
import { ApolloClient, InMemoryCache, HttpLink } from "@apollo/client" (CJS)	41.94 KB (0%)
import { ApolloClient, InMemoryCache, HttpLink } from "@apollo/client" (production) (CJS)	37.49 KB (0%)
import { ApolloClient, InMemoryCache, HttpLink } from "@apollo/client"	32.3 KB (0%)
import { ApolloClient, InMemoryCache, HttpLink } from "@apollo/client" (production)	27.21 KB (0%)
import { ApolloProvider } from "@apollo/client/react"	5.19 KB (0%)
import { ApolloProvider } from "@apollo/client/react" (production)	963 B (0%)
import { useQuery } from "@apollo/client/react"	10.38 KB (0%)
import { useQuery } from "@apollo/client/react" (production)	6.13 KB (0%)
import { useLazyQuery } from "@apollo/client/react"	6.35 KB (0%)
import { useLazyQuery } from "@apollo/client/react" (production)	2.12 KB (0%)
import { useMutation } from "@apollo/client/react"	5.73 KB (0%)
import { useMutation } from "@apollo/client/react" (production)	1.48 KB (0%)
import { useSubscription } from "@apollo/client/react"	6.08 KB (0%)
import { useSubscription } from "@apollo/client/react" (production)	1.83 KB (0%)
import { useSuspenseQuery } from "@apollo/client/react"	7.81 KB (0%)
import { useSuspenseQuery } from "@apollo/client/react" (production)	3.58 KB (0%)
import { useBackgroundQuery } from "@apollo/client/react"	7.64 KB (0%)
import { useBackgroundQuery } from "@apollo/client/react" (production)	3.41 KB (0%)
import { useLoadableQuery } from "@apollo/client/react"	7.63 KB (0%)
import { useLoadableQuery } from "@apollo/client/react" (production)	3.39 KB (0%)
import { useReadQuery } from "@apollo/client/react"	5.86 KB (0%)
import { useReadQuery } from "@apollo/client/react" (production)	1.61 KB (0%)
import { useFragment } from "@apollo/client/react"	5.91 KB (0%)
import { useFragment } from "@apollo/client/react" (production)	1.68 KB (0%)

[phryneas]

We decided off-channel that it makes sense to actually merge this one, so I'll give it a merge :)