The existing NullableType has been deprecated 5 years ago and causes
crashes in Kotlin apps because Kotlin doesn't recognize this annotation
as a nullable type annotation.
While we can't align on a single @Nullable annotation yet, we can at
least replace this one by JSR305's @Nonnull(MAYBE) as it fulfils all
requirements, including full Kotlin compatiblity. To avoid the
cumbersome name, we can redefine it as our own @NullableType
annotation. (We can't use @Nullable to avoid name clashes with the main
@Nullable annotation from AndroidX)
Issue: google/ExoPlayer#6792
PiperOrigin-RevId: 540497469
51fb72b00d