move more reusable logic into toolkit package

[thomasheyenbrock]

In particular we move over:

• Async helper functions (promises, observables and async-iterables)
• Formatting functions for result JSON and errors

I also noticed that the shouldPersistHeaders property that is part of the fetcher options is never used for anything, and after searching through issues and commit history I found no good reason why they should be in there. (@acao maybe I'm lacking context here?) This PR deprecates it and intends to remove it in the next major version of graphiql.

[changeset-bot]

🦋 Changeset detected

Latest commit: 80f772c

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

This PR includes changesets to release 2 packages

Name	Type
graphiql	Patch
@graphiql/toolkit	Patch

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[codecov]

Codecov Report

Merging #2401 (80f772c) into main (2d91916) will decrease coverage by 0.81%.
The diff coverage is 69.48%.

@@            Coverage Diff             @@
##             main    #2401      +/-   ##
==========================================
- Coverage   65.70%   64.89%   -0.82%     
==========================================
  Files          85       81       -4     
  Lines        5106     5278     +172     
  Branches     1631     1703      +72     
==========================================
+ Hits         3355     3425      +70     
- Misses       1747     1849     +102     
  Partials        4        4              

Impacted Files	Coverage Δ
packages/codemirror-graphql/src/hint.ts	94.73% <ø> (ø)
packages/codemirror-graphql/src/lint.ts	100.00% <ø> (ø)
packages/codemirror-graphql/src/results/mode.ts	47.05% <ø> (ø)
...kages/codemirror-graphql/src/utils/forEachState.ts	100.00% <ø> (ø)
packages/codemirror-graphql/src/utils/hintList.ts	95.65% <ø> (ø)
...ackages/codemirror-graphql/src/utils/info-addon.ts	1.02% <ø> (ø)
...ckages/codemirror-graphql/src/utils/mode-indent.ts	0.00% <0.00%> (ø)
packages/codemirror-graphql/src/variables/hint.ts	89.70% <ø> (ø)
packages/codemirror-graphql/src/variables/mode.ts	79.48% <ø> (ø)
.../graphiql/src/components/DocExplorer/Directive.tsx	100.00% <ø> (ø)
... and 83 more

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