8335637: Add explicit non-null return value expectations to Object.toString()
------------- Commit messages: - Backport 66db71563c3ebd715a1192a9b399b618d7bdb8d0 Changes: https://git.openjdk.org/jdk/pull/20124/files Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=20124&range=00 Issue: https://bugs.openjdk.org/browse/JDK-8335637 Stats: 4 lines in 1 file changed: 4 ins; 0 del; 0 mod Patch: https://git.openjdk.org/jdk/pull/20124.diff Fetch: git fetch https://git.openjdk.org/jdk.git pull/20124/head:pull/20124 PR: https://git.openjdk.org/jdk/pull/20124
