R1:01572d9d933b

Implement "Repository" as a new-style CustomField in Differential

Summary:
Ref T3886. Ref T418.

- Adds new capabilities for CustomField:
- Controls can now bulk-load PHIDs (e.g., for tokenizers).
- Transactions can now bulk-load PHIDs (e.g., for relationship changes).
- Implements "Repository" control.
- Improves tokenizer StandardCustomField controls.

Test Plan:
{F115942}

{F115943}

Reviewers: btrahan

Reviewed By: btrahan

CC: aran

Maniphest Tasks: T418, T3886

Differential Revision…