Multiple managed-namespace

# Summary

With the [managed-namespace](https://argoproj.github.io/argo-workflows/managed-namespace/) installation,
would it be possible to manage multiple namespaces ?

# Use Cases

On a single cluster, I have differents teams and each one of them handle multiple products.
And I would want each team to handle her own argo workflow installation for multiple products.
Because one install by product is to heavy, and with a cluster install there is no enough isolation.

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**Message from the maintainers**:

Impacted by this bug? Give it a 👍. We prioritise the issues with the most 👍.

Start with the managed-namespace installation documentation linked in the issue and trace the corresponding installation and namespace-management entry points. Determine how multiple namespaces would affect isolation and team ownership, then verify that the proposed behavior is documented and covered by appropriate tests; the linked pull request should also be reviewed for prior context.

Written by the indexing model from the issue text.