Previously, when building a layered jar with Gradle, project
dependencies were treated the same as any other dependency, being
included in the dependencies or snapshot dependencies layer based
on their version.

This commit updates the default layering when using Gradle to include
project dependencies in the application layer by default. The DSL has
also been updated to allow their layer to be customized using new
includeProjectDependencies() and excludeProjectDependencies() methods
rather than relying on including and excluding them via a
group:artifact:version pattern.

Closes gh-23431