Add mapping for CheckForNull to JSpecify annotation

[zbynek]

What's changed?

When migrating to JSpecify. javax.annotation.CheckForNull is now replaced by org.jspecify.annotations.Nullable.
Semantically CheckForNull is closer to org.jspecify.annotations.Nullable than javax.annotation.Nullable is (see StackOverflow), so this is a safe change.

What's your motivation?

• The recipe should remove all null-related annotations that belong to javax.annotation to avoid manual steps.
• Currently the recipe changes @CheckForNull Object[] to Object @CheckForNull[], but then fails to replace it, resulting in code that does not compile (the old annotation does not have TYPE_USE target).

Anything in particular you'd like reviewers to focus on?

🤷

Anyone you would like to review specifically?

🤷

Have you considered any alternatives or workarounds?

Make a custom .yml recipe.

Any additional context

Projects using SpotBugs for null analysis likely prefer @CheckForNull over javax.annotation.Nullable, so they might benefit from this change.

Checklist

• I've added unit tests to cover both positive and negative cases
• I've read and applied the recipe conventions and best practices
• I've used the IntelliJ IDEA auto-formatter on affected files

[zbynek]

./gradlew test --tests "*JSpecifyBestPracticesTest"

succeeds but

./gradlew test

fails locally -- most of the failed tests seem to be related to openrewrite/rewrite#8355 -- @timtebeek looped.

[timtebeek]

Thanks a lot, also for the helpful link explaining the nuances. I've rebased and will merge when CI succeeds