Support transferring names in bulk

[JeremyRand]

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

Alice has 20 names in a BDB wallet. She would like to move them all to a Descriptor wallet so that the BDB wallet can be retired. Clicking the Configure Name button 20 times is annoying.

Describe the solution you'd like

Add a "Transfer Names" button to the "Manage Names" page, similar to "Renew Names", which allows operating on multiple names. It launches a dialog that accepts a pasteable list of destination addresses. Values remain unchanged.

Describe alternatives you've considered

Alice could code a custom Bash script or something for this, but she would prefer to use the GUI.

I suppose the same effect could be achieved with a "Sweep keys" feature that works with names; I'm open to that approach instead if preferred.

Additional context
N/A.

[JeremyRand]

FWIW I'm not specifically advocating this feature; the "sweep" alternative seems reasonable to me; I'm just relaying this from #529 (comment) since the discussion belongs in its own issue, not cluttering #529.

[JeremyRand]

FWIW I'm not specifically advocating this feature; the "sweep" alternative seems reasonable to me.

Pondered it more and I now think sweeping private keys is not a reasonable approach, because it requires moving private key material around; this is incompatible with some security models (e.g. if different wallets are in different trust domains). So yes I am now specifically advocating this feature.