### Is there an existing issue for this?

- [X] I have searched the existing issues

### Current Behavior

In AWS, DescribeSubnet Response returns:
```
<?xml version="1.0" encoding="UTF-8"?>\n
    <Response>
        <Errors>
            <Error>
                <Code>InvalidSubnetID.NotFound</Code>
                <Message>The subnet ID \'test\' does not exist</Message>
            </Error>
        </Errors>
    <RequestID>f6d041c1-1c96-4720-af30-77745504e2ba</RequestID>
</Response>
```

whereas localstack returns:
```
<?xml version=\'1.0\' encoding=\'utf-8\'?>\n<Errors xmlns="http://ec2.amazonaws.com/doc/2016-11-15">
    <Error>
        <Code>InvalidSubnetID.NotFound</Code>
        <Message>aaThe subnet ID \'vpc-test\' does not exist</Message>
    </Error>
    <RequestID>EADJHWMM796CI5FT10XGFMGOXIPCBAHBWINMV0HR6SKBRODGCU5J</RequestID>
</Errors>

```

### Expected Behavior

It should return correct response structure. It causes terraform to complain.

### How are you starting LocalStack?

Custom (please describe below)

### Steps To Reproduce

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

    make start

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

     awslocal ec2 describe-subnets --subnet-ids vpc-test --debug


### Environment

```markdown
- OS: M1 MacOS
- LocalStack: 1.0.2.dev
```


### Anything else?

Probably `call_moto` function in `localstack/services/moto.py` is changing the error code structure.
# Don't serialize a non-existing map
            return
        if shape.serialization.get("flattened"):
            entries_node = xmlnode
            entry_node_name = name
        else:
            entries_node = ETree.SubElement(xmlnode, name)
            entry_node_name = "entry"
        for key, value in params.items():
            ue is None:
                # Don't serialize any param whose value is None.
                continue
            entry_node = ETree.SubElement(entries_node, entry_node_name)
            key_name = self._get_serialized_name(shape.key, default_name="key")
            val_name = self._get_serialized_name(shape.value, default_name="value")
            self._serialize(shape.key, key, entry_node, key_name)
            self._serialize(shape.value, value, entry_node, val_name)
    @staticmethod
    def _serialize_type_boolean(xmlnode: ETree.Element, params: bool, _, name: str) -> None:
        """
        Fo actually just a scalar value representing the data
        we need to serialize as a boolean. It will either be 'true' or 'false'
        """
        node = ETree.SubElement(xmlnode, name)
        if params:
            str_value = "true"
        else:
            str_value = "false"
        node.text = str_value
    def _serialize_type_blob(