Support `--context` and `--as`

[bear-redhat]

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Is your feature request related to a problem? We are managing multiple clusters, and all of them are using sudo to run privileged operations. Currently, the CLI does not support switching cluster and switching users. The former one makes our lives harder and the second issue actually rendered many subcommands of the CLI useless (since it cannot execute privileged operations).

Describe the solution you'd like

1. support --context parameter to switch contexts
2. support --as parameter to assume users

Describe alternatives you've considered N/A

Additional context N/A

[aantn]

@bear-redhat is this still relevant? We have support for the context already, right? Do you still need --as?