Ignore minimized Desktop apps in Overview.

For each desktop session, Overview shows a single tile with multiple
desktop tasks. With this CL avoid showing minimized tasks in that tile.

Bug: 333013317
Flag: com.android.window.flags.enable_desktop_windowing_mode
Test: manual: ensured minimized desktop tasks are not shown in Overview

Change-Id: I48cb6826849abf225c0fe4448ca7b0b13afea44e