Add "wgMFShowRedLinks" and "wgMFShowRedLinksAnon" config

"wgMFShowRedLinks" and "wgMFShowRedLinksAnon" controls when redlinks for
non existing page links will be removed and when displayed.

Bug: 65640
Change-Id: I8760ee24e4b28643518e446c78a68c6fa451a57c
Merge "Add "wgMFShowRedLinks" and "wgMFShowRedLinksAnon" config"