Switch package manager to pnpm and upgrade to Storybook 8

[ndelangen]

What I did:

@ghengeveld requested this to be upgraded to storybook 8.x in order to use the visual regression addon.,

• I ran the storybook upgrade command
• I ran some manual migrations
• I applied some manual fixes
• Migrated the repo to use pnpm
• tweaked the CI so it uses pnpm

📦 Published PR as canary version: 11.4.1--canary.987.9175126545.0

✨ Test out this PR locally via:

npm install chromatic@11.4.1--canary.987.9175126545.0
# or 
yarn add chromatic@11.4.1--canary.987.9175126545.0

[codacy-production]

Coverage summary from Codacy

See diff coverage on Codacy

Coverage variation	Diff coverage
Report missing for 764456e1	❌ 46.15% (target: 80.00%)

Coverage variation details

	Coverable lines	Covered lines	Coverage
Common ancestor commit (764456e)	Report Missing	Report Missing	Report Missing
Head commit (97d57bc)	8451	6663	78.84%

Coverage variation is the difference between the coverage for the head and common ancestor commits of the pull request branch: <coverage of head commit> - <coverage of common ancestor commit>

Diff coverage details

	Coverable lines	Covered lines	Diff coverage
Pull request (#987)	13	6	46.15%

Diff coverage is the percentage of lines that are covered by tests out of the coverable lines that the pull request added or modified: <covered lines added or modified>/<coverable lines added or modified> * 100%

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Footnotes

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[thafryer]

@ndelangen What led to us using PNPM here? If you were just experimenting, I will ignore. :) Updating to Yarn 4 is very welcome though if you just wanted to update to a newer package manager.

[ghengeveld]

This PR seems to be doing more than upgrade Storybook and the package manager. Ideally this change should not affect the CLI functionally.

[ethriel3695]

This PR seems to be doing more than upgrade Storybook and the package manager. Ideally this change should not affect the CLI functionally.

@ghengeveld some changes were necessary to get tests to pass after changing to pnpm.

Other changes were due to Typescript yelling at me. I've reverted those.