[MM-54770] Add ability to export profile pictures and fix importing them (#25042)

* add ability to export pp and fix import

* remove unused nopSeeker

* remove debug log

* fix shadow vars

* generate a warning instead of an error when unable to export profile picture

* fix merge conflicts

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Co-authored-by: Mattermost Build <build@mattermost.com>

server/public/model/bulk_export.go

@@ -9,6 +9,7 @@ const ExportDataDir = "data"
 
 type BulkExportOpts struct {
 	IncludeAttachments      bool
+	IncludeProfilePictures  bool
 	IncludeArchivedChannels bool
 	CreateArchive           bool
 }