RFR: 8299296: Write a test to verify the components selection sends ItemEvent [v2]

[Ravi Gupta]

> This testcase verifies the following assertions
> 
> a. Selecting an item in the Choice using mouse generates ItemEvent.
> b. Single-click on an Checkbox generates ItemEvent.
> 
> Testing:
> Tested using Mach5(20 times per platform) in macos, linux and windows and got all pass.

Ravi Gupta has updated the pull request incrementally with one additional commit since the last revision:

  8299296: Review Fixes

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Changes:
  - all: https://git.openjdk.org/jdk/pull/11786/files
  - new: https://git.openjdk.org/jdk/pull/11786/files/0f436cad..e02b3d27

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=11786&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=11786&range=00-01

  Stats: 10 lines in 1 file changed: 7 ins; 0 del; 3 mod
  Patch: https://git.openjdk.org/jdk/pull/11786.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/11786/head:pull/11786

PR: https://git.openjdk.org/jdk/pull/11786