Remove deprecated mNonDecorFrame and mConfigFrame

Since insets decoupled is enabled, the fields are always the
same as display frame, so simply use the known size and
remove the duplicated size info.

Bug: 409608996
Flag: EXEMPT remove leftover of insets_decoupled_configuration
Test: DisplayPolicyInsetsTests
Change-Id: Ie44800f78801f5b0fdc64dcb5586286945747d77