Remove some defunct old-style transaction policy checks

Summary:
Ref PHI193. This method of enforcing policy checks is now (mostly) obsolete, and they're generally checked at the Controller/API level instead.

Notably, this method does not call adjustObjectForPolicyChecks(...) properly, so it can not handle special cases like "creating a project and taking its newly created members into account" for object policies like "Project Members".

Just remove these checks, which are redundant with checks elsewhere.

Test Plan:

• Set Project application default edit policy to "Administrators and Project Members".
• Tried to create a project as a non-administrator, adding myself.
• Before patch: policy fatal on a VOID object (the project with no PHID generated yet).
• After patch: object created properly. Got a sensible policy error if I didn't include myself as a member.
• Also verified that other edit rules are still enforced/respected (I can't edit stuff I shouldn't be able to edit).
• There's at least a bit of unit test coverage of this, too, which I updated to work via API (which hits the new broad capability checks) instead of via low-level transactions (which enforce only a subset of policy operations now).

Reviewers: amckinley

Reviewed By: amckinley

Differential Revision: https://secure.phabricator.com/D18763