RFR: 8283774: TestZoneOffset::test_immutable should ignore ZoneOffset::rules [v2]

[Claes Redestad]

> - Add capability to ignore fields explicitly when checking for immutability of classes in java.time
> - Use this to avoid a test failure due the new `rules` cache in `ZoneOffset`
> - Remove `TestZoneOffset` from problem list.

Claes Redestad has updated the pull request incrementally with one additional commit since the last revision:

  Copyrights

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Changes:
  - all: https://git.openjdk.java.net/jdk/pull/7989/files
  - new: https://git.openjdk.java.net/jdk/pull/7989/files/44a8cc6b..4da4429b

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=7989&range=01
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=7989&range=00-01

  Stats: 2 lines in 2 files changed: 0 ins; 0 del; 2 mod
  Patch: https://git.openjdk.java.net/jdk/pull/7989.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/7989/head:pull/7989

PR: https://git.openjdk.java.net/jdk/pull/7989