Added MultipleChoiceAutoCompleteAnswerView, other text field in MCQ answers

[saiful-apx]

• Added MultipleChoiceAutoCompleteAnswerView where developers can pass list of auto complete suggestions, helpful for showing a long list of answers where we can show important choices in the textChoices field and the rest in suggestions.
• Added otherField = true/false/null for both MultipleChoiceAutoCompleteAnswerView and MultipleChoiceAnswerView, this will enable a TextField to input customized answers which is not in the textChoices list.

Additional small updates:

• Replaced PlatformAppBar with Flutter default AppBar for consistency.
• Replaced IconButton for navigating back to Flutter default BackButton widget.

Example Json format:

{
            "stepIdentifier": {
                "id": "13"
            },
            "type": "question",
            "title": "Medicines",
            "answerFormat": {
                "type": "multiple_auto_complete",
                "otherField": true,
                "textChoices": [{
                        "text": "Penicillin",
                        "value": "Penicillin"
                    },
                    {
                        "text": "Latex",
                        "value": "Latex"
                    }

                ],
                "suggestions": [{
                        "text": "Pet",
                        "value": "Pet"
                    },
                    {
                        "text": "Pollen",
                        "value": "Pollen"
                    }
                ]
            }
        },

Demo: