`velero backup download` command could not download other resources except BackupContents

[qiuming-best]

What steps did you take and what happened: [A clear and concise description of what the bug is, and what commands you ran.) For command velero backup download we can only download BackupContents kind of resources, it needs to add a new flag to specify other kinds of resources instead of the default BackupContents here is the code

What did you expect to happen:

The following information will help us better understand what's going on:

If you are using velero v1.7.0+:
Please use velero debug --backup <backupname> --restore <restorename> to generate the support bundle, and attach to this issue, more options please refer to velero debug --help

If you are using earlier versions:
Please provide the output of the following commands (Pasting long output into a GitHub gist or other pastebin is fine.)

• kubectl logs deployment/velero -n velero
• velero backup describe <backupname> or kubectl get backup/<backupname> -n velero -o yaml
• velero backup logs <backupname>
• velero restore describe <restorename> or kubectl get restore/<restorename> -n velero -o yaml
• velero restore logs <restorename>

Anything else you would like to add: [Miscellaneous information that will assist in solving the issue.]

Environment:

• Velero version (use velero version):
• Velero features (use velero client config get features):
• Kubernetes version (use kubectl version):
• Kubernetes installer & version:
• Cloud provider or hardware configuration:
• OS (e.g. from /etc/os-release):

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[cleverhu]

I'd like to improve this, can this issue be assigned to me?

[cleverhu]

@qiuming-best I have pulled a request for this. /PTAL. Thanks.

[qiuming-best]

@cleverhu thanks for your contribution

[Lyndon-Li]

Let's brainstorm the scenarios that other kinds are required to be downloaded and what are the exact kinds required to be downloaded