Remove WindowStateTransactionItem pooling (3/n).

Remove the use of ObjectPool in the creation and management of
WindowStateTransactionItem, WindowStateInsetsControlChangeItem, and
WindowStateResizeItem objects. Instead of being obtained from the pool,
these objects are now directly instantiated, simplifying their handling
and aligning with the broader removal of the object pooling mechanism.

Bug: 311089192
Test: atest FrameworksCoreTests:ClientTransactionItemTest
Flag: EXEMPT removing com.android.window.flags.disable_object_pool
Change-Id: I47e8b2454f4c76ebef5af063b4803ed05ca18259