[a11y] voice message improvements (#5980)

* A11Y: ensure a11y focus is not lost and reset to the back button when the user start playing a pending voice message.

* A11Y: ensure a11y focus is not lost and reset to the back button when the user use the keyboard to focus the send button and press the space bar to perform a click.

* Cleanup code. This if was not necessary.

* Small rework to prepare a bugfix. No behavior / UI change.

* Ensure that the keyboard focus and accessibility focus is not lost when deleting a pending voice message.

* Update screenshots

* Improve code readability.

* Update screenshots

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Co-authored-by: ElementBot <android@element.io>

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