Reduce code duplication in Herald fields

Summary:
Ref T8726. I want to modularize values and reduce how hard-coded / copypasta'd they are.

  - Rename `get...StandardCondition()` to `get...StandardType()`, since we can drive both conditions and values from it.
  - Rename `STANDARD_LIST` to `STANDARD_PHID_LIST` for consistency: all "lists" are lists of PHIDs.
  - For all standard types which don't require typehaeads, lift their logic into the base class.
  - I'll lift typeaheads soon, but need to generalize them first.

Test Plan: Edited various Herald rules, saw value UI generate correctly.

Reviewers: btrahan

Reviewed By: btrahan

Subscribers: epriestley

Maniphest Tasks: T8726

Differential Revision: https://secure.phabricator.com/D13612

src/applications/spaces/herald/HeraldSpaceField.php

@@ -16,7 +16,7 @@ final class HeraldSpaceField extends HeraldField {
     return PhabricatorSpacesNamespaceQuery::getObjectSpacePHID($object);
   }
 
-  protected function getHeraldFieldStandardConditions() {
+  protected function getHeraldFieldStandardType() {
     return self::STANDARD_PHID;
   }