[jdk17u-dev] RFR: 8296275: Write a test to verify setAccelerator method of JMenuItem

[Amos]

- Backport of [JDK-8296275](https://bugs.openjdk.org/browse/JDK-8296275)
- Test succeeded in local dev box

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Commit messages:
 - Backport b005013a0015656b7f6ccc26f8a13c44d61f77b9

Changes: https://git.openjdk.org/jdk17u-dev/pull/1877/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk17u-dev&pr=1877&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8296275
  Stats: 119 lines in 1 file changed: 119 ins; 0 del; 0 mod
  Patch: https://git.openjdk.org/jdk17u-dev/pull/1877.diff
  Fetch: git fetch https://git.openjdk.org/jdk17u-dev.git pull/1877/head:pull/1877

PR: https://git.openjdk.org/jdk17u-dev/pull/1877