chore: use pnpm install mode with Yarn

[kurtdoherty]

Updates our Yarn install mode to pnpm rather than the current node-modules. This brings us some improvements: https://yarnpkg.com/features/linkers#nodelinker-pnpm

This change picked up ghost dependency imports (imports from @storybook/react which is not a direct dependency of the package). These have all been fixed.

[rpt-uk-github]

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[codacy-production]

Coverage summary from Codacy

See diff coverage on Codacy

Coverage variation	Diff coverage
Report missing for f8e08821	✅ ∅

Coverage variation details

	Coverable lines	Covered lines	Coverage
Common ancestor commit (f8e0882)	Report Missing	Report Missing	Report Missing
Head commit (72f3e60)	9325	8631	92.56%

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 (#797)	0	0	∅ (not applicable)

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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