[jdk11u-dev] RFR: 8286872: Refactor add/modify notification icon (TrayIcon)

[Goetz Lindenmaier]

I backport this for parity with 11.0.18-oracle.

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Commit messages:
 - Backport 9f562ef7546c80e6ddce7b932f3f5ca17c741d21

Changes: https://git.openjdk.org/jdk11u-dev/pull/1513/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk11u-dev&pr=1513&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8286872
  Stats: 26 lines in 2 files changed: 14 ins; 5 del; 7 mod
  Patch: https://git.openjdk.org/jdk11u-dev/pull/1513.diff
  Fetch: git fetch https://git.openjdk.org/jdk11u-dev pull/1513/head:pull/1513

PR: https://git.openjdk.org/jdk11u-dev/pull/1513