RFR: JDK-8310571: Use inline @return tag on java.util.Objects

[Joe Darcy]

Small cleanup, minor differences in the wording of portions of toString(Object, String), nonNull(Object), requireNonNullElse, and requireNonNullElseGet.

-------------

Commit messages:
 - JDK-8310571: Use inline @return tag on java.util.Objects

Changes: https://git.openjdk.org/jdk/pull/14608/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=14608&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8310571
  Stats: 41 lines in 1 file changed: 0 ins; 21 del; 20 mod
  Patch: https://git.openjdk.org/jdk/pull/14608.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/14608/head:pull/14608

PR: https://git.openjdk.org/jdk/pull/14608