Make not imported methods java->swift unavailable #228
Description
Missing methods from javakit imports can be sometimes confusing when someone tries to "just use" the library emitted.
We should instead still emit methods, but make them unavailable:
warning: Unable to translate 'org.apache.commons.csv.CSVParser' method 'getRecords': Java class 'org.apache.commons.csv.CSVRecord' has not been translated into Swift
->
@available(*, unavailable, message: "Java class 'org.apache.commons.csv.CSVRecord' has not been translated into Swift")
etc