Fix cold-lauch Activity Embeded apps flash black.

Before collect new created task fragment in createTaskFragment(),
recomputeConfiguration() will set a crop in PendingTransaction,which
will cause starting window be cropped before staring window reparent
to root task in SyncTransaction.So addToSyncSet() before
recomputeConfiguration().

Test: pressure test cold-lauch Activity Embeded apps and no flash black.
Bug: b/324148725

Change-Id: I7ded9adb1c52d61b700edfdc83e7929cff67e529