RFR: 8329705: Add missing Application thread checks to platform specific a11y methods

[Kevin Rushforth]

On Thu, 4 Apr 2024 21:55:11 GMT, Alexander Zuev <kizune at openjdk.org> wrote:

> Added missing checks;
> Added a manual regression test;

Both the fix and the test look good. Testing complete on Mac and Windows.

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Marked as reviewed by kcr (Lead).

PR Review: https://git.openjdk.org/jfx/pull/1436#pullrequestreview-1983807637