Cloudformation - DescribeStacksErrorKind only contains "Unhandled"

### Describe the bug

The [DescribeStacksErrorKind](https://github.com/awslabs/aws-sdk-rust/blob/31cfae2cf23be0c68a47357070dea1aee9227e3a/sdk/cloudformation/src/error.rs#L3858-L3861) only contains the value "Unhandled", and it is necessary to match against the error string to decide how to respond to an error. For instance, a quick way to check if a stack exists is to use this call to list, filtering for the given stack name, and then checking that the error returned indicates the stack doesn't exist.

### Expected Behavior

The known responses to be parsed out and exposed as different `kind`s to avoid the caller having to do this themselves (like the other APIs?)

### Current Behavior

Code like this:

```rust
return if e.to_string().contains("does not exist") {
Ok(false)
} else {
// This is less great
...
}
```

### Reproduction Steps

call DescribeStacks and try and parse the response

### Possible Solution

Parse the response out to the different types within the SDK

### Additional Information/Context

_No response_

### Version

```text
0.21.0
```

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

osx 12.5.1

### Logs

_No response_

Start in sdk/cloudformation/src/error.rs around DescribeStacksErrorKind and inspect how DescribeStacks responses are represented. Compare the handling with other APIs mentioned in the issue, then identify the known error responses that should be exposed as distinct kinds. Done means callers can distinguish the relevant responses without matching error strings.

Written by the indexing model from the issue text.