[amp-story-player] Audit public API methods for layout state

[Enriqe]

We should audit the public methods of the player for layout state.

In #34360, I found that by calling play() under certain circumstances (player hidden, and no user scroll), the player can break. We should investigate other public methods to see if they will work correctly (e.g. show(), add(), etc..).

/cc @ampproject/wg-stories

[stale]

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