[jdk17u-dev] RFR: 8330815: Use pattern matching for instanceof in KeepAliveCache

[Christoph Langer]

Nearly clean backport from 21u-dev, only copyright conflicts. Will mark as clean.

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

Commit messages:
 - Backport ddecbe52018fdb7556b04b20e8529eb430d3aa75

Changes: https://git.openjdk.org/jdk17u-dev/pull/2464/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk17u-dev&pr=2464&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8330815
  Stats: 4 lines in 1 file changed: 0 ins; 0 del; 4 mod
  Patch: https://git.openjdk.org/jdk17u-dev/pull/2464.diff
  Fetch: git fetch https://git.openjdk.org/jdk17u-dev.git pull/2464/head:pull/2464

PR: https://git.openjdk.org/jdk17u-dev/pull/2464