Replace Collections.emptyXXX with Immutable Static Factory Methods

[mkarg]

• This is similar to Replace Collections.singletonXXX with Immutable Static Factory Methods #72

Replace

List<String> list = Collections.emptyList()
Map<String,String> map = Collections.emptyMap();
Set<String> set = Collections.emptySet();

With

List<String> list =  List.of()
Map<String,String> map = Map.of();
Set<String> set  = Set.of();