Adapt to native-image reflection changes

[mhalbritter]

GraalVM has some changes regarding reflection lined up:

1. Querying methods, ctors, fields, etc. enabled by default for registered classes
2. Throw exception if metadata is missing

Until 1. is done, we should not tackle 2, as 1. will remove a lot of places where 2. would fail.

When 1. is done, Spring Framework needs to adapt the RuntimeHints API to use the new metadata field.

For reference, Spring Framework already did some adaption related to this in spring-projects/spring-framework#31213.

[mhalbritter]

There's also this new --strict-image-heap, which shouldn't affect us that much as we don't rely on build time init.

[mhalbritter]

Issue on GraalVM side: oracle/graalvm-reachability-metadata#499