Fix ImageWallpaper memory regression

Scale bitmap to fit display size leads to memory regression, this cl
removes the sacling logic and also disable wallpaper transitions when
the bitmap size is smaller than display size to avoid broken visual.

Bug: 147379974
Bug: 145897588
Bug: 124838911
Test: Manually
Test: atest com.android.systemui.ImageWallpaperTest
--rerun-until-failure 20
Test: atest com.android.systemui
Change-Id: I243274af54538fc89268c448aa2c5a95f63c7ae3