(lambda): Add `domain` helper prop to FunctionUrl

### Describe the feature

The lambda.FunctionUrl construct currently returns the Function URL as a full URL including the scheme + trailing `/`.

`https://*******.lambda-url.ap-southeast-2.on.aws/`

In many cases, it's preferable to have just the domain name.

`*******.lambda-url.ap-southeast-2.on.aws`

### Use Case

When serving a Function URL through a Cloudfront Distribution. The following workaround is required to remove the URL Scheme and path from `fn_url.url` so it can be consumed by `Cloudfront.HttpOrigin`

```python
fn_url = function.add_function_url(
auth_type=lmbda.FunctionUrlAuthType.NONE,
)

# This removes the URL Scheme and trailing `/` from the Function URL`
# leaving: "*******.lambda-url.ap-southeast-2.on.aws"
fn_url_domain = Fn.select(
0, Fn.split("/", Fn.select(1, Fn.split("https://", fn_url.url)))
)

distribution = cf.Distribution(
self,
"distribution",
default_behavior=cf.BehaviorOptions(
origin=cfo.HttpOrigin(fn_url_domain),
)
)
```

### Proposed Solution

The above code be added as a helper function on FunctionUrl construct:

```
fn_url_domain = Fn.select(
0, Fn.split("/", Fn.select(1, Fn.split("https://", fn_url.url)))
)
```

### Other Information

Happy to implement this one if it's a wanted change. Open to any suggestions on code or property names etc.

### Acknowledgements

- [X] I may be able to implement this feature request
- [ ] This feature might incur a breaking change

### CDK version used

2.50.0

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

MacOS 13