Enable new build options for GraalVM 25 native image builds

[bclozel]

As of GraalVM 25 and the generation of the new metadata format in Spring Framework 7.0, we should ensure that native image builds with the Spring Boot build plugins configure by default the following options: --exact-reachability-metadata (for the new metadata format) and --future-defaults=all (to prepare for future releases).

[bclozel]

Reverting because this is breaking integration tests. Let's figure out later if we need changes in default build options, then.