As part of the upgrade, this commit removes the use of any API that
has been deprecated in 2.9.0.pr1. This includes the config props
endpoint's use of SerializationFeature.WRITE_NULL_MAP_VALUES. This
has been replaced with configuring serialization inclusion to only
include properties with non-null values. This means that all
null-valued properties will no longer be serialized, not just those
that are an entry in a map.
Closes gh-8604
Closes gh-8537
10ae5e8f3f