### Is there an existing issue for this?

- [X] I have searched the existing issues

### Current Behavior

when executing the commands from this issue
* #5293

specifically the last command: 

    aws --debug --endpoint-url="http://localhost:4566" sqs change-message-visibility --queue-url http://localhost:4566/000000000000/MyQueue --receipt-handle garbage --visibility-timeout 30

i get the following XML response:
```xml
<ErrorResponse xmlns="http://queue.amazonaws.com/doc/2012-11-05/"><Error><Code>ReceiptHandleIsInvalid</Code><Message>The input receipt handle "garbage" is not a valid receipt handle.</Message></Error><RequestId>RC7Q6J8V0LJ4EN2WQXGANXA2XWRL13D4GN6NVJF1V8UFBAVEO417</RequestId></ErrorResponse>
```
and the following headers:
```python
{
    'Content-Type': 'text/plain; charset=utf-8',
    'Content-Length': '309',
    'Access-Control-Allow-Origin': '*',
    'Access-Control-Allow-Methods': 'HEAD,GET,PUT,POST,DELETE,OPTIONS,PATCH',
    'Access-Control-Allow-Headers': 'authorization,cache-control,content-length,content-md5,content-type,etag,location,x-amz-acl,x-amz-content-sha256,x-amz-date,x-amz-request-id,x-amz-security-token,x-amz-tagging,x-amz-target,x-amz-user-agent,x-amz-version-id,x-amzn-requestid,x-localstack-target,amz-sdk-invocation-id,amz-sdk-request',
    'Access-Control-Expose-Headers': 'etag,x-amz-version-id',
    'Connection': 'close',
    'date': 'Tue, 18 Jan 2022 23:17:17 GMT',
    'server': 'hypercorn-h11',
}

```

this XML has three issues:
1. there's no `<?xml` start declaration
2. the message content is not HTML encoded (`"` should be `&quot;`)
3. the content type is `text/plain`

### Expected Behavior

The XML returned by AWS looks as follows:
```xml
<?xml version="1.0"?><ErrorResponse xmlns="http://queue.amazonaws.com/doc/2012-11-05/"><Error><Type>Sender</Type><Code>ReceiptHandleIsInvalid</Code><Message>The input receipt handle &quot;garbage&quot; is not a valid receipt handle.</Message><Detail/></Error><RequestId>bd34a56b-d17a-552a-b343-ff0b22169609</RequestId></ErrorResponse>
```
with the following response headers:
```python
{
    'x-amzn-RequestId': '3e3ad214-7356-536b-8342-88753f3af4f7',
    'Date': 'Tue, 18 Jan 2022 23:15:56 GMT',
    'Content-Type': 'text/xml',
    'Content-Length': '334',
}
```

### How are you starting LocalStack?

With the `localstack` script

### Steps To Reproduce

#### How are you starting localstack (e.g., `bin/localstack` command, arguments, or `docker-compose.yml`)

    PROVIDER_OVERRIDE_SQS=asf DEBUG=1 python -m localstack.cli.main start --host

#### Client commands (e.g., AWS SDK code snippet, or sequence of "awslocal" commands)

```
aws --endpoint-url="http://localhost:4566" sqs create-queue --queue-name MyQueue
aws --debug --endpoint-url="http://localhost:4566" sqs change-message-visibility --queue-url http://localhost:4566/000000000000/MyQueue --receipt-handle garbage --visibility-timeout 30
```

### Environment

```markdown
- OS: Linux Mint 20
- LocalStack: latest
```

### Anything else?

Not sure this is really the root cause of #5293, but worth investigating and fixing regardless.
_botocore_serializer_integration_test("sqs", "SetQueueAttributes", {})
def test_query_serializer_sqs_flattened_list_with_botocore():
    response = {
        "QueueUrls": [
            "http://localhost:4566/000000000000/myqueue1",
            "http://localhost:4566/000000000000/myqueue2",
        ]
    }
    _botocore_serializer_integration_test("sqs", "ListQueues", response)
def test_query_serializer_sqs_flattened_map_with_botocore():
    response = {
        "Attributes": {
            "QueueArn": "arn:aws:sqs:us-east-1:000000000000:test-queue-01",
            "DelaySeconds": "0",
        }
    }
    _botocore_serializer_integration_test("sqs", "GetQueueAttributes", response)
def test_query_serializer_sqs_flattened_list_map_with_botocore():
    response = {
        "Messages": [
            {
                "MessageId": "ac9baa5c-13b1-4206-aa28-2ac45ae168af",
                "ReceiptHandle": "AQEBZ14sCjWJuot0T8G2Eg3S8C+sJGg+QRKYCJjfd8iiOsrPfUzbXSjlQquT9NZP1Mxxkcud3HcaxvS7I1gxoM9MSjbpenKgkti8TPCc7nQBUk9y6xXYWlhysjgAi9YjExUIxO2ozYZuwyksOvIxS4NZs2aBctyR74N3XjOO/t8GByAz2u7KR5vYJu418Y9apAuYB1n6ZZ6aE1NrjIK9mjGCKSqE3YxN5SNkKXf1zRwTUjq8cE73F7cK7DBXNFWBTZSYkLLnFg/QuqKh0dfwGgLseeKhHUxw2KiP9qH4kvXBn2UdeI8jkFMbPERiSf2KMrGKyMCtz3jL+YVRYkB4BB0hx15Brrgo/zhePXHbT692VxKF98MIMQc/v+dc6aewQZldjuq6ANrp4RM+LdjlTPg7ow==",
                "MD5OfBody": "13c0c73bbf11056450c43bf3159b3585",
                "Body": '{"foo": "bared"}',
            }
        ]
    }
    _botocore_serializer_integration_test("sqs", "ReceiveMessage", response)
def test_query_serializer_sqs_none_value_in_map():