R1:17e1732152ae

Route all ManiphestTransaction reads through a single class

Summary:
Ref T2217. I'm going to do the fake-double-writes ("double reads"?) thing where we proxy the storage that worked pretty well for auth. That is:

- (Some more cleanup diffs next, maybe?)
- Move all the data to the new storage, and make `ManiphestTransaction` read and write by wrapping `ManiphestTransactionPro`.
- If nothing breaks, it's a straight shot to nuking ManiphestTransaction callsite by callsite.

I think Maniphest is way…