Move TaskThumbnailViewData initialisation to init.

This is because onLayout can be called before onAttachedToWindow so this property needs to be initialised as it is used in onLayout.

Fix:  383733481
Flag: com.android.launcher3.enable_refactor_task_thumbnail
Test: Manual checking of split select and incorrect orientation for now but will be tested by view screenshot tests.

Change-Id: I40937b8b1b98209e77cb5ee64f5c4342b90faf97