public void addMarkupNestedFuncs() {
		Markup ma = field.getAnnotation(Markup.class);
		if (ma != null) {
			Class<?> fieldType = field.getType();
			if (!ReflectionHelper.hasStructureMapping(fieldType)) {
				throw new IllegalArgumentException("Invalid @Markup, %s is not structure mapped. %s"
						.formatted(field.getType().getSimpleName(), field));
			}
			markupFuncs.add(this::markupNestedStructure);
		}
	}
Creates a FieldMappingInfo instance, used when the structure is variable length and there is
no pre-defined Ghidra Structure data type.

@param <T> structure mapped class type
@param field java field
@param fieldName name of Ghidra structure field
@param signedness {@link Signedness} enum
@param length override of structure field, or -1
@return new {@link FieldMappingInfo} instance
Ghidra/Features/Base/src/main/java/ghidra/app/util/bin/format/golang/structmapping/FieldMappingInfo.java