Enhance download member to support multi-select

[JWaters02]

Is your feature request related to a problem? Please describe.

Suggested during the systems demo. Can either download a single member or all members of a PDS, but not a selection of members.

Describe the solution you'd like

Support multiselect to download a selection of members

Describe alternatives you've considered

Download all members and delete the ones not needed.

Additional context

[github-actions]

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