Extend the AWS CodeArtifact login command to support multiple namespaces

### Describe the feature

I propose enhancing the `aws codeartifact login` command to allow for multiple namespaces to be specified in a single command.
This could be implemented by allowing the `--namespace` flag to accept a list of namespaces instead of a single value.

### Use Case

Currently, the AWS CodeArtifact login command restricts users to specify a single namespace per login attempt.
This limitation requires users to execute multiple login commands, or manually configure other scopes/namespaces when working with projects that depend on packages from multiple private namespaces within the same domain.

### Proposed Solution

Example of the proposed command usage:

```shell
aws codeartifact login \
--tool npm \
--repository my-repository \
--domain my-domain \
--namespace @namespace-a,@namespace-b,@namespace-c
```

### Other Information

### Related Issues

- #5404

### Acknowledgements

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

### CLI version used

aws-cli/2.15.28

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

Sonoma 14.2.1