Refactor Inset tests to use WindowStateBuilder

Combining multiple classes since the changes are small
- ImeInsetsSourceProviderTest
- InsetsPolicyTest
- InsetsSourceProviderTest
- InsetsStateControllerTest

Bug: 383480021
Test: atest WmTests:ImeInsetsSourceProviderTest
Test: atest WmTests:InsetsPolicyTest
Test: atest WmTests:InsetsSourceProviderTest
Test: atest WmTests:InsetsStateControllerTest
Flag: EXEMPT cleaning up tests
Change-Id: I4b89d3f14bf7da457b9ec9674ce06fa430357c79