Not encoding Unicode characters in json output can lead to `UnicodeEncodeError`.

### Describe the bug

I queried a dynamoDB and asked for json output. The result contained Unicode chars that cannot be encoded in cp1252, the default character encoding for console applications on Windows. This raised a `UnicodeEncodeError` in AWS CLI halfway through the output.

### Expected Behavior

AWS CLI should output valid json and not throw an exception, regardless of what the encoding is for stdout.

### Current Behavior

AWS CLI explicitly tells the json encoder to _not_ ensure all output characters are in ASCII range:
https://github.com/aws/aws-cli/blob/develop/awscli/formatter.py#L95
```
json.dump(response, stream, indent=4, default=json_encoder,
ensure_ascii=False)
```
The json encoder will consequently not encode Unicode characters and try to write them to stdout:
https://github.com/python/cpython/blob/main/Lib/json/__init__.py#L179
```
for chunk in iterable:
fp.write(chunk)
```
At this point, the Unicode characters will automatically be encoded to whatever encoding stdout is using. On Windows, this is commonly [cp1252](https://en.wikipedia.org/wiki/Windows-1252), which does not cover the entire Unicode range. If the output contains any Unicode characters that cannot be encoded, it will raise a `UnicodeEncodeError`.

### Reproduction Steps

1. Create a dynamoDB table with a field that contains a Unicode character that cannot be encoded in cp1252, such as "⚠".
2. Run this command `aws dynamodb scan --table-name --output json`

### Possible Solution

Allow json output to be ASCII only. Either by default, or through a command-line flag.

### Additional Information/Context

_No response_

### CLI version used

aws-cli/2.3.0 Python/3.8.8 Windows/10 exe/AMD64 prompt/off

### Environment details (OS name and version, etc.)

Windows 10 20H2 (OS Build 19042.1645), Python 3.10.0