The `ignore_malformed` option is supported by a few of our field types, mainly numerics and dates, to still accept the document when such fields hold malformed values. See https://www.elastic.co/guide/en/elasticsearch/reference/current/ignore-malformed.html. Also `ignore_malformed` is an index level setting that gets applied to all field types that support it. 

The boolean field type does not support `ignore_malformed` but it should, so that if a boolean field cannot be parsed as a boolean, the document can still be accepted.


server/src/test/java/org/elasticsearch/index/mapper/BooleanFieldMapperTests.java
@Override
    protected Object getSampleValueForDocument() {
        return true;
    }
    @Override
    protected void minimalMapping(XContentBuilder b) throws IOException {
        b.field("type", "boolean");
    }
    @Override
    protected void registerParameters(ParameterChecker checker) throws IOException {
        checker.registerConflictCheck("doc_values", b -> b.field("doc_values", false));
        checker.registerConflictCheck("index", b -> b.field("index", false));
        checker.registerConflictCheck("store", b -> b.field("store", true));
        checker.registerConflictCheck("null_value", b -> b.field("null_value", true));
    }
    public void testExistsQueryDocValuesDisabled() throws IOException {
        MapperService mapperService = createMapperService(fieldMapping(b -> {
            minimalMapping(b);
            b.field("doc_values", false);
        }));
        assertExistsQuery(mapperService);
        assertParseMinimalWarnings();
    }
    public void testAggregationsDocValuesDisabled() throws IOException {
        MapperService mapperService = createMapperService(fieldMapping(b -> {
            minimalMapping(b);