feat: add async List APIs for DataStore and API

[lawmicha]

Issue #, if available:

Description of changes: This is based on the async APIs for APIPlugin (https://github.com/aws-amplify/amplify-ios/pull/2140) and async APIs for DataStore. This PR adds the async versions of the APIs for List such as fetch, load, getNextPage.

Check points: (check or cross out if not relevant)

• [ ] Added new tests to cover change, if needed
• [ ] Build succeeds with all target using Swift Package Manager
• [ ] All unit tests pass
• [ ] All integration tests pass
• [ ] Security oriented best practices and standards are followed (e.g. using input sanitization, principle of least privilege, etc)
• [ ] Documentation update for the change if required
• [ ] PR title conforms to conventional commit style
• [ ] If breaking change, documentation/changelog update with migration instructions

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