Avoid page_restrictions field queries for templates on edit form

Avoid page_restrictions field queries for templates on edit form

* Title::newFromRow() will actually load page_restrictions, which
  should normally be empty. This avoids queries in getRestrictions().
  Those queries could add 100-200ms to edit form views.
* getLinksFrom() has been simplified to use newFromRow(), thus
  loading the old restrictions in passing.

Change-Id: I225955589a82e4accbf059d17390a5e28e2fa1ca