Create separate @rjsf/utils package

[epicfaace]

Original comment:

I say we break out the utils package since it'll be better to maintain that way. If we need to make a path or minor to the utils package, in theory it shouldn't break anyones installs if they are using a ^ (i.e. "@rjsf/utils": "^X.X.X").

For the fields and widgets, they should probably just be exposed in the root index file still so you can import them like so:

import { ArrayField } from '@rjsf/core';`

We would just need to ensure tree shaking is set up correctly, that way they don't import everything from @rjsf/core.

Originally posted by @chanceaclark in #1642

[epicfaace]

Fixed by #1641.

[heath-freenome]

Fixed in the v5 beta, see the 5.x migration guide