Allow annotation values to be included in nonPublicMarkers

[juliamcclellan]

In AndroidX we would like to exclude some APIs from compatibility tracking based on the androidx.annotation.RestrictTo annotation. RestrictTo is used with a Scope value, e.g. @RestrictTo(LIBRARY_GROUP).

Only some scopes should be excluded from compatibility tracking, so we'd like to use something like androidx.annotation.RestrictTo(androidx.annotation.RestrictTo.Scope.LIBRARY) in nonPublicMarkers to filter APIs annotated @RestrictTo(LIBRARY) but not APIs annotated @RestrictTo(LIBRARY_GROUP) (or other scope values).