[jdk11u-dev] RFR: 8302525: Write a test to check various components send Events while mouse and key are used simultaneously

[Amos]

- Backport of [JDK-8302525](https://bugs.openjdk.org/browse/JDK-8302525)
- Test succeeded in local dev box

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Commit messages:
 - Backport c7517b3decdc55edb7f0ce6e6aa09a6b653c747d

Changes: https://git.openjdk.org/jdk11u-dev/pull/2184/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk11u-dev&pr=2184&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8302525
  Stats: 556 lines in 1 file changed: 556 ins; 0 del; 0 mod
  Patch: https://git.openjdk.org/jdk11u-dev/pull/2184.diff
  Fetch: git fetch https://git.openjdk.org/jdk11u-dev.git pull/2184/head:pull/2184

PR: https://git.openjdk.org/jdk11u-dev/pull/2184