[GR-49525] Mechanism to move JDK initialization to run time.

[graalvmbot]

We are reducing build-time initialization of the JDK in following GraalVM versions. This means that many substitutions for run-time-initialized parts of the JDK will not be needed anymore.

Problems:

1. If previously initialized classes end up in the image heap of user code, they will break the build.
2. The projects that build-time initialize the whole world will need the JDK substitutions.

How to avoid code breakage

We introduce -H:+InitializeJDKAtBuildTimeMigration that will keep the previous initialization functionality. This flag will simply enable a feature that build-time initializes the same set of classes as the previous GraalVM versions.

The build-time initialization error message would be augmented with a note that they can use the previous behavior with -H:+InitializeJDKAtBuildTimeMigration until they introduce all required -initialize-at-build-time=<class>.

How to support build-time initialized projects

Introduce a separate package for build-time initialization substitutions and make them available only if the class is initialized at build time.

This will require a slight change in the way we handle TargetClass:

@TargetClass(value = java.lang.SecurityManager.class, onlyWith = MarkedAsBuildTimeInitialized.class)

If needed we will provide an API for markedAsBuildTimeInitialized in RuntimeClassInitialization.

This package will be maintained by the GraalVM team until the JDK initialization minimization is complete. After that, it would be handed over for maintenance to the community.

The same package would be moved into a spearate community maintained project when we remove -H:+MigrationInitializeJDKAtBuildTime.

Example usage: #10537

[jerboaa]

@vjovanov Could you please add a description to this PR? It shows up empty over here :-/