feat(data): API V6 migration; 'core' util and config mapping updates; add API 'generateClient' and types; migrate subscription provider; REST client updates

[david-mcafee]

Description of changes

This PR includes the following changes:

• Migration of api-v6 work (with some simplification)
• Updates to configuration of api, api-graphql, and api-rest
• Updates to parseAWSExports to include config mapping for the API category (including multiple auth modes)
• Type updates
• Updates to api, api-graphql, and api-rest to use fetchAuthSession and use the new Amplify singleton
• Internal API category code has been trimmed down to exclude logic that is not being used by generateClient
• Addition of core singleton types for the API category
• Migration from PubSub to AWSAppSyncRealTimeProvider (with updates)
• REST API updates
• Resource config + library options types for API
• Dependency resolutions have been added to unblock regeneration of yarn.lock file

Issue #, if available

Description of how you validated changes

Checklist

• PR description included
• yarn test passes (NOTE: Some tests have been disabled. Updating tests to work with V6 will be a fast-follow)
• Tests are changed or added
• Relevant documentation is changed or added (and PR referenced)

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.