Allow passing numeric or string resource ID in new CLI

[spetz]

In order to make a new CLI compatible with existing API, we could allow the user to provide either numeric ID (e.g. Stream = 1), or string ID (e.g. Topic = "orders") for the resources such as stream, topic and user.

For example, the SDK command looks like this:

pub struct DeleteTopic {
    pub stream_id: Identifier,
    pub topic_id: Identifier,
} 

And the CLI command could either use the same Identifier wrapper or just make use of String? to work similarly:

pub(crate) struct TopicDelete {
    stream_id: u32,
    topic_id: u32,
}

The only exceptions are CreateStream and CreateTopic commands (in the latter, you can use the Identifier for stream_id only).