Export missing for JVM typealias decls

[tomdaffurn]

Any typealias defined in Java and used in a verb should be exported, but isn't. e.g. javamodule has these:

 typealias AnySerializedType Any  
    +typemap java "xyz.block.ftl.test.AnySerializedType"
    +typemap go "github.com/blockxyz/ftl/test.AnySerializedType"
  typealias CustomSerializedType String  
    +typemap java "xyz.block.ftl.test.CustomSerializedType"
    
  export verb anyAliasedType(javamodule.AnySerializedType) javamodule.AnySerializedType

Bug is caused by two bits of code knowing partial information about the type alias. TypeAliasProcessor creates the typealias decl, but doesn't know to export it. VerbProcessor knows to export it, but doesn't update the decl.