R1:604d1409f16f

Make buildPagingClauseFromMultipleColumns() safer

Summary: Ref T7803. Reduce the amount of code we're trusting to build SQL queries.

Test Plan:
- Paged through results in Maniphest, Differential and Diffusion.
- Some of the NULLable groups in Maniphest are a bit funky but this was preexisting.

Reviewers: btrahan

Reviewed By: btrahan

Subscribers: epriestley

Maniphest Tasks: T7803

Differential Revision: https://secure.phabricator.com/D12353