RFR: 8288137: The set of available printers is not updated without application restart

[Phil Race]

This fixes the issue that the default printer or set of available printers is fixed from the first call to it in the lifetime of the application.
Now subsequent calls will check to see if there are changes.
A manual test is provided for verifying this - it requires you to add/remove printers at the system level to verify anything related to this fix.

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Commit messages:
 - 8288137
 - 8288137
 - 8288137

Changes: https://git.openjdk.org/jfx/pull/817/files
 Webrev: https://webrevs.openjdk.org/?repo=jfx&pr=817&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8288137
  Stats: 216 lines in 3 files changed: 199 ins; 3 del; 14 mod
  Patch: https://git.openjdk.org/jfx/pull/817.diff
  Fetch: git fetch https://git.openjdk.org/jfx pull/817/head:pull/817

PR: https://git.openjdk.org/jfx/pull/817