Clean fails to clean orphaned build files

### Affected version

3.5.0 et al

### Bug description

Clean currently misses generated files that are .gitignored and relics of previous builds after the pom.xml that built them is deleted.

See

https://github.com/apache/maven-resolver/issues/1943
https://github.com/apache/maven/issues/11800

related but not the same: https://issues.apache.org/jira/browse/RAT-476 (Fixing this bug would keep the RAT plugin from failing a build based on the gitignored files, but would not remove them. They would remain uncleaned in the project directory.)

"The Clean Plugin is used when you want to remove files generated at build-time in a project's directory."

Are there files generated at build-time in a project's directory? Yes.
Is the clean plugin failing to remove them? Yes.

Start by reading the clean behavior described here and the linked Maven Resolver and Maven issues, then locate the clean plugin's handling of generated and ignored files. Verify the behavior with a project whose generating pom.xml is removed; done means clean removes the orphaned build files from the project directory.

Written by the indexing model from the issue text.