[CLI] Provide ability to independently set data_stream.namespace from --space

[BenB196]

Today, when you use the CLI and set the --space value, it will set the value for data_stream.namespace as well. You should be allowed to independently set the value of data_stream.namespace.

If you attempt something like:

heartbeat.monitors:
  - type: icmp
    data_stream:
      namespace: "public.default.development"
    name: google.com
    id: google.com
    enabled: true
    hosts:
      - "google.com."
    schedule: "@every 20s"

And run the command

npx @elastic/synthetics push --yes --id icmp-development --space observability --private-locations 'S0000 - Development'

You get the error:

✖ Error
   > Unsupported Heartbeat option: monitor(tstrtr01.heroes.bayada.com)
       The following Heartbeat options are not supported for icmp project monitors in 8.6.2: data_stream.namespace. You monitor was not created or updated.

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Use Case

If you want to have a number of different monitors in the same space, but want to have different retention times on them, you need to use something like data_stream.namespace to differentiate the data.