Allow Spring Boot to print the classpath SBOM

[blaghed]

With native images, and starting with GraalVM 23, it is possible to include the SBOM file in the classpath by running the build with --enable-sbom=classpath.
It would be handy to have a standard approach to view/print this SBOM file on demand.

Discussion in #40630 suggests an approach via -Djarmode=tools.
Examples:
my-app -Djarmode=tools sbom
java -Djarmode=tools -jar my-app.jar sbom
java -Djarmode=tools -jar my-app.jar sbom [--destination my-app.sbom.json] (toggle between System.out or a file)

[mhalbritter]

We are also supporting creation of SBOM files via the CycloneDX plugins and could print them, too.

One thing to note here is that Spring Boot application binaries created with native-image don't have the jarmode jar on the classpath - we'd need to invent something else for that.