8.0.0-M3 - `@Configuration` classes registered in `resources.groovy` are not processed by a `ConfigurationClassPostProcessor` anymore

### Expected Behavior

`@Configuration` classes registered in `resources.groovy` are processed by a `ConfigurationClassPostProcessor`.

### Actual Behaviour

`@Configuration` classes registered in `resources.groovy` are not processed by a `ConfigurationClassPostProcessor` anymore.

* from taking a look at the grails-8 plugin bean registration changes (which are great btw.), i think that the `ConfigurationClassPostProcessor`registered in `CoreGrailsPlugin` now runs before an apps' `resources.groovy` beans are registered?
* ref. https://github.com/apache/grails-core/blob/v8.0.0-M3/grails-core/src/main/groovy/org/grails/plugins/CoreGrailsPlugin.groovy#L75-L76

### Steps To Reproduce

* run grails-8 sample app
* no "sample bean registered" console out
* run grails-7 sample app
* "sample bean registered" console out

### Environment Information

* grails-8.0.0-M3 (vs. grails-7.2.1)
* ubuntu-24.04
* jdk-21

### Example Application

* grails-8.0.0-M3: https://github.com/zyro23/grails-core-16029-grails-8
* grails-7.2.1: https://github.com/zyro23/grails-core-16029-grails-7

### Version

8.0.0-M3

Start with CoreGrailsPlugin.groovy at lines 75-76 and trace how beans from resources.groovy are registered. Compare the Grails 8 and Grails 7 sample applications and their reproduction steps, then verify that the Grails 8 sample prints "sample bean registered" like Grails 7.

Written by the indexing model from the issue text.