Allow access to Lists fields and other metadata from Backend API

[MurzNN]

After Keystone's core was reworked by #5665, we miss the ability to access Lists metadata at backend side.

For example, earlier we can get list of fields from needed List via something like this:

const myListFields = context.lists[listName].fieldsByPath;
const myListAuthorFieldType = context.lists[listName].fieldsByPath['author'].adapter.fieldName; // eg 'Relationship'

This PR is returns ability to get list of fields for all Lists, with all metadata such as field type (kind), access, hooks, views, etc:

const myListAuthorFieldType = context.initialisedLists[listName].fields['author'].dbField.kind; // 'relation'

Please review id and describe if something wrong... Or if this info is already accessible at backend via some API call, please show some examples. Thanks!

[changeset-bot]

🦋 Changeset detected

Latest commit: 9cc7399

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 10 packages

Name	Type
@keystone-next/keystone	Minor
@keystone-next/auth	Major
@keystone-next/example-testing	Patch
@keystone-next/example-with-auth	Patch
@keystone-next/example-auth	Patch
@keystone-next/examples-app-basic	Patch
@keystone-next/example-ecommerce	Patch
keystone-next-app	Patch
@keystone-next/example-roles	Patch
@keystone-next/example-sandbox	Patch

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[timleslie]

Implemented in #6403.