[AppBarLayout] Does not expand when used with a nested CoordinatorLayout on version > 1.2.1

还没有人认领这个 Issue。

**Description:** When we use a CoordinatorLayout nested inside another CoordinatorLayout and we define different scroll flags for each AppBarLayout, it doesn't work properly in 1.2.1 version (and 1.3.0-rc01). Note that it works correctly on 1.0.0 version.
The goal is to have an AppBarLayout with a CollapsingToolbar (scrollFlags scroll|exitUntilCollapsed|snap) in the main CoordinatorLayout and an AppBarLayout with a Toolbar (scrollFlags scroll|enterAlways|snap) in the nested CoordinatorLayout.

| Version 1.0.0 (Works as expected) | Version 1.2.1 and above (Not working) |
|---|---|
|  |  |

**Source code:**

Project:
https://github.com/serbelga/NestedCoordinatorLayout

Layout:
https://github.com/serbelga/NestedCoordinatorLayout/blob/24d3012553ab917df35360157c0654be4dfd638d/app/src/main/res/layout/activity_coordinator.xml#L32-L52

**Android API version:** Android API 30

**Material Library version:** 1.2.1

从链接的 NestedCoordinatorLayout 复现以及 app/src/main/res/layout/activity_coordinator.xml 第 32-52 行开始，在 Android API 30 上比较 Material Library 1.0.0 与 1.2.1 或更高版本之间的行为。跟踪嵌套的 CoordinatorLayout 与 AppBarLayout 之间的交互；当外层 CollapsingToolbar 和内层 Toolbar 遵循各自不同的滚动标志，并像正常工作的版本一样展开或折叠时，即表示完成。

由索引模型根据 Issue 内容生成。