[MaterialToolbar] Shadow is drawn over content with the same elevation

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**Description:** The shadow from a `MaterialToolbar` will draw over content below it even if it is of the same elevation. For example, if I have a `MaterialCardView` with `cardElevation=4dp` that is directly below a `MaterialToolbar` with `elevation=4dp`, there will be a shadow cast on the `MaterialCardView` from the `MaterialToolbar`.

**Expected behavior:** I would expect that there is no shadow over the card, since it is the same elevation as the app bar.

**Source code:** Modify `cat_topappbar_action_bar_activity.xml` from the catalog app so that the contents is within a `MaterialCardView`:
```xml

```

Then open the Action Bar Demo in the Catalog app.


**Android API version:** 31

**Material Library version:** 1.7.0-beta01

**Device:** Google Pixel 4a

Reproduce the issue by updating cat_topappbar_action_bar_activity.xml in the catalog app with the provided MaterialCardView, then open the Action Bar Demo. Trace how MaterialToolbar elevation and its shadow are rendered relative to the card. Done means content at the same 4dp elevation no longer receives a visible toolbar shadow.

Written by the indexing model from the issue text.