8353007: Open some JComboBox bugs 2

[satyenme]

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Backporting JDK-8353007: Open some JComboBox bugs 2. Adds four JComboBox tests. Ran GHA Sanity Checks and new tests directly. Patch is clean. Backporting for parity with Oracle.

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Progress

• [x] Change must not contain extraneous whitespace
• [x] Commit message must refer to an issue
• [x] JDK-8353007 needs maintainer approval

Issue

• JDK-8353007: Open some JComboBox bugs 2 (Bug - P4 - Approved)

Reviewing

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$ git fetch https://git.openjdk.org/jdk17u-dev.git pull/4146/head:pull/4146
$ git checkout pull/4146

Update a local copy of the PR:
$ git checkout pull/4146
$ git pull https://git.openjdk.org/jdk17u-dev.git pull/4146/head

Using Skara CLI tools

Checkout this PR locally:
$ git pr checkout 4146

View PR using the GUI difftool:
$ git pr show -t 4146

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https://git.openjdk.org/jdk17u-dev/pull/4146.diff

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