Backport 14.6: Support HST serving a Campaign version of a document

See https://docs.google.com/document/d/1BGThfhu-X2Ls_GaPr9CcRPOY2jxMybfN8YZyU373uv8

When rendering a document (in general any document, not just XPage Docs, however the FE UI only supports setting 'campaign' on XPage Docs), the HST will

1. Check which 'campaigns' from the 3-Tuple on the handle node have a date range which matches the current server time
2. Filter the matches on existing version nodes with a branchId which matches the requested branch (missing branchId means master)
3. From the matches, use the one with the shortest 'live range' since this is arguably the most relevant one