Make repository identity email address association case-insensitive

Summary:
Ref T13444. Currently, identities for a particular email address are queried with "LIKE" against a binary column, which makes the query case-sensitive.

  - Extract the email address into a separate "sort255" column.
  - Add a key for it.
  - Make the query a standard "IN (%Ls)" query.
  - Deal with weird cases where an email address is 10000 bytes long or full of binary junk.

Test Plan:
  - Ran migration, inspected database for general sanity.
  - Ran query script in T13444, saw it return the same hits for "git@" and "GIT@".

Subscribers: PHID-OPKG-gm6ozazyms6q6i22gyam

Maniphest Tasks: T13444

Differential Revision: https://secure.phabricator.com/D20907

src/applications/diffusion/controller/DiffusionRepositoryListController.php

@@ -17,6 +17,14 @@ final class DiffusionRepositoryListController extends DiffusionController {
       ->setName(pht('Browse Commits'))
       ->setHref($this->getApplicationURI('commit/'));
 
+    $items[] = id(new PHUIListItemView())
+      ->setType(PHUIListItemView::TYPE_LABEL)
+      ->setName(pht('Identities'));
+
+    $items[] = id(new PHUIListItemView())
+      ->setName(pht('Browse Identities'))
+      ->setHref($this->getApplicationURI('identity/'));
+
     return id(new PhabricatorRepositorySearchEngine())
       ->setController($this)
       ->setNavigationItems($items)