Treat freeform and fullscreen tasks as compatible.

In some scenarios where shell changes the windowing mode of fullscreen
launch to freeform, the activity would be launched on a seperate task
instead of the existing freeform task in recents.

This cl makes it so that we treat freeform and fullscreen as same.

Fix: 368515903
Test: atest RecentTasksTest
Flag: EXEMPT Bugfix
Change-Id: I168fe64a0574eede709d928b6b855eb81ec31ae3