Support for macro table appends in binary 1.1 reader

[jobarr-amzn]

This test case fails when added to EncodingDirectiveCompilationTest:

    @ParameterizedTest(name = "{0},{1}")
    @MethodSource("allCombinations")
    public void macroAppendWithoutMacros(InputType inputType, StreamType streamType) throws Exception {
        ByteArrayOutputStream out = new ByteArrayOutputStream();
        IonRawWriter_1_1 writer = streamType.newWriter(out);
        writer.writeIVM();

        startEncodingDirective(writer);
        startMacroTable(writer);
        writer.writeSymbol(SystemSymbols_1_1.ION_ENCODING);
        endMacroTable(writer);
        endEncodingDirective(writer);

        byte[] data = getBytes(writer, out);
        try (IonReader reader = inputType.newReader(data)) {
           assertNull(reader.next());
        }
    }

This is equivalent to:

$ion_encoding::( (macro_table $ion_encoding) )

[jobarr-amzn]

Partially fixed by #976, but now this test fails:

    @ParameterizedTest(name = "{0},{1}")
    @MethodSource("allCombinations")
    public void macroAppendWithoutMacros(InputType inputType, StreamType streamType) throws Exception {
        ByteArrayOutputStream out = new ByteArrayOutputStream();
        IonRawWriter_1_1 writer = streamType.newWriter(out);
        writer.writeIVM();

        SortedMap<String, Macro> macroTable = new TreeMap<>();
        macroTable.put("foo", new TemplateMacro(
          Collections.singletonList(new Macro.Parameter("foo", Macro.ParameterEncoding.Tagged, Macro.ParameterCardinality.ExactlyOne)),
          Collections.singletonList(new Expression.VariableRef(0))
        ));
        Map<String, Integer> symbols = Collections.emptyMap();

        // $ion_encoding::(
        //   ( macro_table (macro foo (x) (%x) ) )
        // )
        startEncodingDirective(writer); {
            startMacroTable(writer); {
                startMacro(writer, symbols, "foo"); {
                    writeMacroSignature(writer, symbols, "x");
                    writeVariableExpansion(writer, symbols, "x");
                } endMacro(writer);
            } endMacroTable(writer);
        } endEncodingDirective(writer);
        
        // $ion_encoding::(
        //   ( macro_table $ion_encoding )
        //   ( symbol_table ["bar"])
        // )
        startEncodingDirective(writer); {
            startMacroTable(writer); {
                writer.writeSymbol(SystemSymbols_1_1.ION_ENCODING);
            } endMacroTable(writer);
            writeEncodingDirectiveSymbolTable(writer, true, "bar");
        } endEncodingDirective(writer);

        // (:0 $1) i.e. (:foo bar)
        writer.stepInEExp(0, true, macroTable.get("foo")); {
            writer.writeSymbol(1);
        } writer.stepOut();

        byte[] data = getBytes(writer, out);
        try (IonReader reader = inputType.newReader(data)) {
           assertEquals(IonType.SYMBOL, reader.next());
           assertEquals("bar", reader.stringValue());
        }
    }

[jobarr-amzn]

The problem comes from this line, where newMacros is installed as the encoding context macro map. newMacros is a field of the EncodingDirectiveReader, which retains the reference and clears the map the before it reads the next encoding directive.