RFR: 8289389: Fix warnings: type should also implement hashCode() since it overrides Object.equals() [v3]

[Andy Goryachev]

> - added missing hashCode() methods

Andy Goryachev has updated the pull request incrementally with one additional commit since the last revision:

  8289389: minimize the impact of collision

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Changes:
  - all: https://git.openjdk.org/jfx/pull/821/files
  - new: https://git.openjdk.org/jfx/pull/821/files/d82e683f..ed53414c

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jfx&pr=821&range=02
 - incr: https://webrevs.openjdk.org/?repo=jfx&pr=821&range=01-02

  Stats: 6 lines in 1 file changed: 0 ins; 4 del; 2 mod
  Patch: https://git.openjdk.org/jfx/pull/821.diff
  Fetch: git fetch https://git.openjdk.org/jfx pull/821/head:pull/821

PR: https://git.openjdk.org/jfx/pull/821