Java: Consider some support for backwards flow through writer wrappers

Consider supporting source to sink flow in the following snippet:
```java
void f(Appendable sink, String source) {
JSONWriter w = new JSONWriter(sink);
w.write(source);
```
Through the model row `"org.json;JSONWriter;true;JSONWriter;;;Argument[-1];Argument[0];taint"`.
Context: https://github.com/github/codeql/pull/6325#discussion_r680984746

Go already has some support for this in https://github.com/github/codeql-go/blob/main/ql/src/semmle/go/dataflow/FunctionInputsAndOutputs.qll#L124.