Adds overrides for common Map operations to avoid having to allocate the entrySet for Collectors$Partition maps.
------------- Commit messages: - Overriding containsKey and containsValue of Collectors - JDK-8170945: override more Map-methods on Collectors Changes: https://git.openjdk.org/jdk/pull/13347/files Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=13347&range=00 Issue: https://bugs.openjdk.org/browse/JDK-8170945 Stats: 29 lines in 1 file changed: 29 ins; 0 del; 0 mod Patch: https://git.openjdk.org/jdk/pull/13347.diff Fetch: git fetch https://git.openjdk.org/jdk.git pull/13347/head:pull/13347 PR: https://git.openjdk.org/jdk/pull/13347
