[TopAppBar] Make compress effect flag available via setScrollEffect

[patrickfrei]

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Is your feature request related to a problem? Yes, this feature request is related to issue #2887

Describe the solution you'd like

1. For com.google.android.material.appbar.MaterialToolbar and androidx.appcompat.widget.Toolbar, a compress effect can be added to the toolbar title in XML by using app:layout_scrollEffect="compress".
2. However, trying to programmatically set that scroll effect (e.g. for certain API levels only) by using setScrollEffect (see documentation) isn't possible. Reason: The scroll effect flag SCROLL_EFFECT_COMPRESS declared in AppBarLayout class is not publicly accessible and can therefore not be set.
3. Currently, a globally set compress effect can just be unset if null is passed to setScrollEffect but not the other way round.
4. Therefore, it would be great to have a possiblity to set the scroll effect "compress" programmatically via setScrollEffect by using the SCROLL_EFFECT_COMPRESS flag.