Move into core to make the core status report messsage useful

Problem/Motivation

See #3132302: Provide an easier way for developers to identify entity/field definition mismatches

Currently, the status message about the mismatches is not very helpful, but even confusing for users and even most developers.
To make it useful, we should consider
a) to move this module into core, once working well
b) linking the contrib module in the warning message, if that's allowed in core

Really awesome work, thank you! This has been a pain until now!

Steps to reproduce

Proposed resolution

Remaining tasks

User interface changes

API changes

Data model changes