[MaterialContainerTransform] View to Activity transition uses incorrect activity position if app is launched in multiwindow mode and placed at the bottom of split screen

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**Description:** View to Activity transition uses incorrect start and end activity position. On enter transition new activity comes from the top of the app window and goes there on exit. Works only if app placed at the bottom of the screen.

**Expected behavior:** Activity transition should work the same in multiwindow mode as in fullscreen.

**Source code:** Reproduced in catalog app.

**Android API version:** Checked on API 26 and 29

**Material Library version:** Tested on 1.2.0-alpha06 and 1.3.0-alpha01

**Device:** Emulators and real devices.

Video from emulator running catalog app. You can see both cases with activity animation works incorrectly while fragment one is good:
https://drive.google.com/file/d/1BIilNsiE4qvF6CGC9dRoI27XtOkAbTru/view?usp=sharing

Reproduce the transition in the catalog app with the activity placed at the bottom of a split-screen window, using the API versions and library versions listed. Compare the activity transition with the working fragment transition and trace how MaterialContainerTransform determines activity positions. Done means the activity animation matches fullscreen behavior in multiwindow mode.

Written by the indexing model from the issue text.