Avoid Java compiler errors around invoking unqualified methods called "yield" in generated decoders in Java 17

[writeoncereadmany]

More recent versions of Java introduce errors when invoking unqualified methods called "yield". For example, in Java 17:

error: invalid use of a restricted identifier 'yield'
        final DecimalFloatDecoder yield = yield();
                                          ^
  (to invoke a method called yield, qualify the yield with a receiver or type name)

Our build process fails on warnings, and builds decoders written using the JavaGenerator.

Those decoders include a appendTo method, which has patterns like:

        final DecimalFloatDecoder yield = yield();
        if (yield != null)
        {
            yield.appendTo(builder);
        }

where the method names are based on the field names. When we have a field called yield - which we need, that's the domain concept, this yields (if you'll pardon the pun) this compiler error.

One simple fix is - if it were instead:

        final DecimalFloatDecoder yield = this.yield();
        if (yield != null)
        {
            yield.appendTo(builder);
        }

it would not raise the error.

I'll start by trying to create a unit test to reproduce the problem.

[writeoncereadmany]

I believe that's all the paths through writeTokenDisplay in JavaGenerator handled with this-qualification, and that's the only place this error can arise. At the very least, this is a start :)

[writeoncereadmany]

Fix merged, thanks