Merge className and intent onto element icons in <Icon>

[ggdouglas]

Summary

• <Icon> now cloneElements a passed React element and merges the parent-provided className and intent class onto its root, instead of returning the element unchanged
• fixes spacing and intent propagation for static icon elements used as the icon prop of Tab, Tree, Section, EntityTitle, NonIdealState, TagInput, and Alert
• implements Option 5 from [RFC] How should core components style static icon elements? #8077; alternative to the per-component wrapper span approach in fix(tag-input): apply icon spacing and color to static icon elements #8067–fix(tabs): wrap static icon elements with tab-icon class for spacing #8073

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Description

Merge className and intent onto element icons in

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[blueprint-previews]

fix(icon): merge className and intent onto element icons

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This is an automated comment from the deploy-preview CircleCI job.

[blueprint-previews]

(temp) Static icon propagation stories

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This is an automated comment from the deploy-preview CircleCI job.

[blueprint-previews]

Revert "(temp) Static icon propagation stories"

Build artifact links for this commit: documentation | landing | table | demo | storybook

This is an automated comment from the deploy-preview CircleCI job.