RFR: 8289389: Fix warnings: type should also implement hashCode() since it overrides Object.equals() [v4]

[Andy Goryachev]

> - added missing hashCode() methods

Andy Goryachev has updated the pull request with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase. The pull request contains five additional commits since the last revision:

 - 8289389: review comments
 - Merge remote-tracking branch 'origin/master' into 8289389.hash
 - 8289389: minimize the impact of collision
 - 8289389: toExternalForm()
 - 8289389: implemented missing hashCode()

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Changes:
  - all: https://git.openjdk.org/jfx/pull/821/files
  - new: https://git.openjdk.org/jfx/pull/821/files/ed53414c..dd9e60a7

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jfx&pr=821&range=03
 - incr: https://webrevs.openjdk.org/?repo=jfx&pr=821&range=02-03

  Stats: 3309 lines in 70 files changed: 2998 ins; 63 del; 248 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