Essentials: Bring measure/outline addons into monorepo

[shilman]

Addon-essentials depends on the measure and outline addons, which are each developed in their own repos. This causes two problems:

1. Two copies of storybook are installed for prerelease users
2. E2E tests failing in CI

Both of these are due to a deficiency in semver where 6.4.0-alpha.x does not match the range ^6.3.0. As far as I know, there is no easy workaround and I believe gaetanmaisse yannbf have explored this a bit.

Duplicate installs

When a user installs 6.4.0-alpha.6, measure/outline will each install their own 6.3.x versions of Storybook. This takes up extra install space/time, but worse could cause compatibility issues in future 6.4.0-alpha.x releases (and certainly in 7.0.0-alpha.x when we get there).

CI failures

In this case, CI publishes monorepo libraries to a Verdaccio server, so all instances of @storybook/x@6.4.0-alpha.x get mapped to the local copies of the libraries, not the ones published publicly in NPM. There is probably a Verdaccio setting to resolve ALL versions of @storybook/x to the local version (including ^6.3.0 as requested by measure/addon). However, if we solve the duplicate install problem by moving the addons into the monorepo, this problem gets solved "for free".

[shilman]

Egads!! I just released https://github.com/storybookjs/storybook/releases/tag/v6.4.0-alpha.13 containing PR #15526 that references this issue. Upgrade today to the @next NPM tag to try it out!

npx sb upgrade --prerelease

Closing this issue. Please re-open if you think there's still more to do.