Fix banner name filter and put it in URLs

Correct bug on Special::CentralNoticeBanners in which banner name
filters disappeared when paging about. Instead of trying to store
the filter in session data, pass it around in a URL query parameter.
This also solves a bug requesting filters in a URL query parameter.

Bug: 39212
Bug: 53753
Change-Id: I7d01c1e4b340ca3f9beee6942e9ceb8768bb208f