[v5] [icons] fix default icon loader, add more built-in webpack loaders

[adidahiya]

Changes proposed in this pull request:

• [icons] Fix a bundle size regression caused by [v5] [icons] feat: reduce bundle size, load paths instead of components #6212
  • In that PR, the default icon loader function was changed to use multiple variables in its import path, which broke the webpack optimization which allowed us to omit generated/components modules from the resulting bundle.
  • This change fixes the default loader function to use two paths which have static parts for the icon sizes (16px and 20px)
• [icons] feat: Add support to IconLoaderOptions for multiple built-in webpack-annotated loaders: "webpack-lazy-once" (default), "webpack-lazy", and "webpack-eager"
• [icons] feat: Add new API Icons.setLoaderOptions() to globally specify an icon loader so that it doesn't have to be set on each call to Icons.load()
• [icons] ⚠️ deprecation: iconNameToPathsRecordKey (use getIconPaths instead)
• [webpack-build-scripts] fix: omit extracted LICENSE.txt comment files from bundler output

Reviewers should focus on:

No regressions in docs-app, demo-app

Screenshot

webpack-bundle-analyzer visualization:

Before	After

[adidahiya]

fix path in generated component file

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

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

[adidahiya]

rename new API

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[adidahiya]

remove references to allPaths

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

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