RFR: 8300977: Retire java.io.ExpiringCache

Wed Mar 22 13:40:35 UTC 2023

This PR proposed to retire the class 'java.io.ExpiringCache'. The use of the class has been off by default since Java 16 but could be explicitly turned on by means of two System properties.

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Commit messages:
 - Remove warnings
 - Update copyright years
 - Retire ExpiringCache

Changes: https://git.openjdk.org/jdk/pull/12167/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=12167&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8300977
  Stats: 446 lines in 6 files changed: 7 ins; 413 del; 26 mod
  Patch: https://git.openjdk.org/jdk/pull/12167.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/12167/head:pull/12167

PR: https://git.openjdk.org/jdk/pull/12167