Always set gnus-group property to a group name

* lisp/gnus/gnus-group.el (gnus-group-prepare-flat-list-dead): Set
gnus-group property to a group name, not active info. (bug#33653)
Simplify surrounding logic.
(gnus-group-prepare-flat, gnus-group-goto-group): Use accessor
macros.
(gnus-group-insert-group-line, gnus-group-new-mail)
(gnus-group-mark-group): Write ?\s instead of ? .
(gnus-group-group-name, gnus-group-list-active): Simplify.
parent bd6a19cc
Pipeline #1254 failed with stage
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