Minor icon cleanup

app/src/main/res/drawable-hdpi/ic_splash.png

app/src/main/res/drawable-mdpi/ic_splash.png

app/src/main/res/drawable-xhdpi/ic_splash.png

app/src/main/res/drawable-xxhdpi/ic_splash.png

app/src/main/res/drawable-xxxhdpi/ic_splash.png

app/src/main/res/mipmap-hdpi/ic_launcher.png

app/src/main/res/mipmap-mdpi/ic_launcher.png

app/src/main/res/mipmap-v26/ic_launcher.xml

app/src/main/res/mipmap-xhdpi/ic_launcher.png

app/src/main/res/mipmap-xxhdpi/ic_launcher.png

app/src/main/res/mipmap-xxxhdpi/ic_launcher.png

app/src/main/res/raw/keep.xml

app/src/main/res/values/mipmap.xml

persistence/build.gradle.kts