Javax annotation dependency @Nonnull should not rely on plugin dependencies

[binkley]

Turning off the Spotbugs plugin in the Maven build breaks the javax annotations (@Nonnull).
The code should not depend on the plugins to compile.

• When the Maven build runs, and SpotBugs is disabled, the build should still compile

Tech analysis

We are missing the javax.annotations dependency, and rely on the spotbugs-annotations dependency to provide them.
Add the dependency, and update the imports, and see if Nonnull got renamed (ie, NonNull, etc).
Otherwise, this is short work.

Further

Turn off all plugins, and check the code compiles.

[jwlibby]

Nothing to review for this, spotbugs is necessary. Also this was only done in a test branch so no changes that broke anything were committed to master