API-1835: add ability to get and list namespaces from must-gather

[deads2k]

Needed to feed operators that get, list, watch namespaces.

[openshift-ci-robot]

@deads2k: This pull request references API-1835 which is a valid jira issue.

Warning: The referenced jira issue has an invalid target version for the target branch this PR targets: expected the epic to target the "4.18.0" version, but no target version was set.

In response to [this](https://github.com/openshift/library-go/pull/1840): >Needed to feed operators that get, list, watch namespaces. > > Instructions for interacting with me using PR comments are available [here](https://prow.ci.openshift.org/command-help?repo=openshift%2Flibrary-go). If you have questions or suggestions related to my behavior, please file an issue against the [openshift-eng/jira-lifecycle-plugin](https://github.com/openshift-eng/jira-lifecycle-plugin/issues/new) repository.

[openshift-ci[bot]]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: bertinatto, deads2k

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[openshift-ci[bot]]

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