This commit adds a `Build-Jdk-Spec` attribute to the manifest in a
jar or war file built with the Spring Boot Gradle plugin. This
aligns the Gradle plugin's behavior with the default Maven plugin
behavior.
This removes the need to set a `BP_JVM_VERSION` environment variable
when invoking Cloud Native Buildpacks, as the Paketo buildpacks will
honor `Build-Jdk-Spec` in a jar or war manifest to determine the
default JVM version.
Fixes gh-32829
This commit adds the `AutoConfigurationImportsAnnotationProcessor` to
the `spring-boot-autoconfigure-processor` annotation processor
module. When added to a project build, the annotation processor will
generate the
`org.springframework.boot.autoconfigure.AutoConfiguration.imports`
file automatically from `@AutoConfiguration`-annotated classes. It
also applies the annotation processor to the Spring Boot build.
Closes gh-31228
