Provide a testing API for the `announce` functionality

[nbayati]

We don't have a testing API for the accessibility announcement function. Applications have to write tests reading the announcement logs and checking it against the expected message using hard-coded values. This is not scalable as we will break the existing tests if we add a new parameter (like PR #107568) or make any changes to the structure of the message dataMap.

We need to provide a testing API that allows the user to check the message and optionally the other parameters like textDirection and assertiveness.

[github-actions]

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