Transactions - kill the old "show all" code pathways

Summary: we still need to be pager-sensitive, but otherwise this "show all" stuff is dead, dead dead...! Ref T4712. I think we can close the book on T4712 with one more diff to clean up the array_reverse / reverse paging stuff? That diff is probably a bit tricky as it involes auditing every TransactionQuery callsite...

Test Plan: viewed a task with a lot of transactions. clicked "show older" and it worked!

Reviewers: epriestley

Reviewed By: epriestley

Subscribers: Korvin, epriestley

Maniphest Tasks: T4712

Differential Revision: https://secure.phabricator.com/D10926