RFR: 8300977: Retire java.io.ExpiringCache [v2]

[Per Minborg]

> 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.

Per Minborg has updated the pull request incrementally with one additional commit since the last revision:

  Revert change after comments

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Changes:
  - all: https://git.openjdk.org/jdk/pull/12167/files
  - new: https://git.openjdk.org/jdk/pull/12167/files/fcc4c96b..105d4583

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=12167&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=12167&range=00-01

  Stats: 5 lines in 1 file changed: 4 ins; 0 del; 1 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