Use stable frame to position freeform windows.

We should generally speaking avoid launching apps behind stable insets
by default, unless either app requests to do it or user has moved the
app to there previously.

Bug: 139274545
Test: ManifestLayoutTests failures indicate windows are put out of
stable insets. Still need CTS fix to finally fix that test case.
Test: atest TaskLaunchParamsModifierTests

Change-Id: I8bc5d23d2ae87f8343aef18023ee7b4fcf9a1bed