[TopAppBar] elevation (on scroll) of top app bar

Nobody has claimed this yet.

**Description:**
https://m3.material.io/components/top-app-bar/specs:
The elevation (on scroll) of top app bar is **3dp**.
```
Element | Design attribute | Role | Token
1. Container | Color | Surface | md.sys.color.surface
| Surface tint color | Surface tint | md.sys.color.surface-tint
| Elevation | Level 0 | md.sys.elevation.level0
| Elevation (on scroll) | Level 2 | md.sys.elevation.level2
```
https://github.com/material-components/material-components-android/blob/master/docs/components/TopAppBar.md:
The elevation of AppBarLayout is 0dp to **4dp**.
The default value of elevation of MaterialToolbar is **not 4dp but 0dp**.
```
Element | Attribute | Related method(s) | Default value
MaterialToolbar elevation | android:elevation | setElevation |
| | getElevation | 4dp
AppBarLayout elevation | android:stateListAnimator | setStateListAnimator |
| | getStateListAnimator | 0dp to 4dp (see all states)
```
Catalog app:
The elevation (on scroll) of top app bar is **4dp**.

Is it a document bug, a catalog bug, or an AppBarLayout bug?

**Source code:**
https://github.com/material-components/material-components-android/blob/master/catalog/java/io/material/catalog/topappbar/res/layout/cat_topappbar_fragment.xml#L25-L38
https://github.com/material-components/material-components-android/blob/master/catalog/java/io/material/catalog/topappbar/res/layout/cat_topappbar_collapsing_medium_fragment.xml#L24-L46
...
https://github.com/material-components/material-components-android/blob/master/lib/java/com/google/android/material/appbar/AppBarLayout.java#L305-L306
https://github.com/material-components/material-components-android/blob/master/lib/java/com/google/android/material/appbar/res/values/dimens.xml#L19
https://github.com/material-components/material-components-android/commit/c587dd12597ee52086c3f637f03d6913e56e03cc

(TopAppBar on Scroll)
(TopAppBar)

**Android API version:** 32

**Material Library version:** 1.5.0, 1.6.0-rc01, 1.7.0-alpha01

**Device:** Emulator 31.2.10

P.S. design_appbar_elevation appears:
https://github.com/material-components/material-components-android/blob/master/lib/java/com/google/android/material/appbar/CollapsingToolbarLayout.java#L793
https://github.com/material-components/material-components-android/blob/master/lib/java/com/google/android/material/appbar/res/animator-v21/design_appbar_state_list_animator.xml#L34
https://github.com/material-components/material-components-android/blob/master/lib/java/com/google/android/material/appbar/res/values/styles.xml#L61
https://github.com/material-components/material-components-android/blob/master/lib/java/com/google/android/material/appbar/res/values/styles.xml#L113

Start with the catalog layouts, AppBarLayout.java, its dimens.xml, and the referenced state-list animator and styles files. Compare the documented, catalog, and library elevation values and check relevant existing tests or rendering behavior. Done means the project has one confirmed, consistent elevation behavior or documentation decision, with coverage or updated references where appropriate.

Written by the indexing model from the issue text.