Use self sync transaction for assignLayer

When finish sync, we merge all sync root memeber's sync transaction
without any ordering. To ensure the ordering, use self sync
transaction whenever possible.

Bug: 310106489
Bug: 388127825
Test: manually test with the reproduce steps in bug
Flag: com.android.window.flags.use_self_sync_transaction_for_layer
Change-Id: I1d8d1f501e323c0bf9e0e07116dd32b4855f9619