Review composite ID field change property type

Problem/Motivation

The `changed` property of the composite UUID fields is created as a signed integer, similar to other Drupal core timestamps. The corresponding validation has been added as a constraint as "-2147483648/2147483648'. We should review this though and see if it makes sense to correct it to be an unsigned integer.

Steps to reproduce

Proposed resolution

Remaining tasks

User interface changes

API changes

Data model changes