Core: Change react deps to normal deps

[ndelangen]

Issue: #11492

This is a proposal for a fix for the above mentioned issue..

Users get warningson missing

What I did

• MOVE all react peer-dep to regular dep, since we use webpack alias to ensure singletons, see:
  

  storybook/lib/core/src/server/preview/iframe-webpack.config.js

  Lines 182 to 187 in 03b5540

  	alias: {
  	...themingPaths,
  	...storybookPaths,
  	...reactPaths,
  	},

  
  and
  

  storybook/lib/core/src/server/manager/manager-webpack.config.js

  Lines 142 to 146 in 298ad9e

  	alias: {
  	...themingPaths,
  	...uiPaths,
  	},
  	plugins: [

This should remove the warnings for users not using react / react-dom

[gaetanmaisse]

react and react-dom are listed in package.json of apps too (as transitive peer deps) so if we move them to regular deps in core packages we can remove them from apps (and that should fix a lot of Yarn/NPM warnings)

[shilman]

This looks good to me, but it also looks like a huge destabilizing change and I'm worried about making it in the RC.

We can:

1. Roll it out & see what happens & potentially roll it back
2. Wait for 6.1 to make the change

I have a preference towards option 1 if everybody agrees this pushes things forward.

[gaetanmaisse]

As it, I'm not sure it will remove all warnings and I think there is not much benefit merging this in RC as everything is working fine for now 🤷 I mean it can wait for 6.1 and be part of a bigger work on deps. But I'm not strongly opinionated, both options look ok 😄 🙈

[ndelangen]

react and react-dom are listed in package.json of apps too (as transitive peer deps) so if we move them to regular deps in core packages we can remove them from apps (and that should fix a lot of Yarn/NPM warnings)

I'll see if I can do that today