Stop importing all of @storybook/icons in @storybook/core

[JReinhold]

For backwards compatibility, @storybook/icon is imported as * in two places:

1. The Icons component in @storybook/core/components: https://github.com/storybookjs/storybook/blob/next/code/core/src/components/components/icon/icon.tsx/#L35-L62 this component is deprecated, and the new icons are supposed to be used and imported individually by users/addon authors

2. The globalisation in @storybook/core/manager/globals: https://github.com/storybookjs/storybook/blob/next/code/core/src/manager/globals/runtime.ts/#L25 Which makes all of @storybook/iconsglobally available in the manager bundle. This ensures that@storybook/icons` is only bundled in once in the manager, but ideally this shouldn't be necessary at all, if icons where imported individually instead.

Currently the components and manager entrypoints of @storybook/core both have all 190kb of @storybook/icons bundled in, which is significant given that icons could instead be imported individually, some being <1kb in size.

• components: https://635781f3500dd2c49e189caf-rjflqvpgls.chromatic.com/?path=/story/bench--es-build-analyzer&args=metafile:core_SLASH_components_DOT_esm_DOT_json
• manager: https://635781f3500dd2c49e189caf-rjflqvpgls.chromatic.com/?path=/story/bench--es-build-analyzer&args=metafile:core_SLASH_manager_DOT_esm_DOT_json

In Storybook 9.0 we should remove these wildcard imports so only the used icons are bundled in.