Annotations for Nonnull, CheckForNull, and several others were proposed
for Java as part of dormant Java specification request JSR-305. The
proposal never became a part of standard Java.

Jenkins plugins should switch from using JSR-305 annotations to use
Spotbugs annotations that provide the same semantics.

The [mailing list discussion](https://groups.google.com/g/jenkinsci-dev/c/uE1wwtVi1W0/m/gLxdEJmlBQAJ)
from James Nord describes the affected annotations and why they should
be replaced with annotations that are actively maintained.

The ["Improve a plugin" tutorial](https://www.jenkins.io/doc/developer/tutorial-improve/replace-jsr-305-annotations/)
provides instructions to perform this change.

An [OpenRewrite recipe](https://docs.openrewrite.org/recipes/jenkins/javaxannotationstospotbugs)
is also available and is even better than the tutorial.

Confirmed that automated tests pass on Linux with Java 21.

Replace JSR-305 annotations with spotbugs annotations

Enable Jenkins Security Scan

Upgrade Jenkins core from 2.361.4 to 2.452.4