Set up addon channel before importing addons

[IanVS]

Fixes storybookjs/storybook#17852

This also re-organizes our virtual filenames a bit, putting them in a single file that can be imported from various spots, rather than having to pass around the strings as extra options.

To fix the issue, I pulled out the code that sets up the addon channel from the "modern" approach, and import that at the start of the non-static-store code. It needed to be a separate file due to the way es module imports work, otherwise addon code will be imported before the channel can be created, if we tried to do it all in one file. Bonus points for getting to share some code between the two approaches, I guess.

[shilman]

@IanVS much cleaner! ❤️

is there any way I can test this easily in the monorepo? i tried downgrading the packages in examples/react to 6.4 (because oddly the error doesn't repro in 6.5?!) but i got a yarn install error.

[shilman]

Nevermind, I had to regenerate the lockfile. Tested and this appears to fix the problem 🎉

[IanVS]

I'm not sure why you would have had to recreate the lock file. Maybe if it happens again, you could try a git clean and a fresh yarn install. Also, when changing react versions, it's best to change them in all examples, otherwise we've seen problems where mixed versions of storybook packages are used due to whatever way yarn does or doesn't hoist.