R1:8268abcb7880

Enrich "diffusion.commit.search" with identity, status, and message information

Summary:
Depends on D19657. Ref T13197. See PHI841.

This enriches the results from `diffusion.commit.search` with information similar to the information returned by the "commits" attachment from `differential.diff.search`.

Also include unreachable, imported, message, audit status, and repository PHID.

Test Plan: Called `diffusion.commit.search` and reviewed the results, which looked sensible.

Reviewers: amckinley

Reviewed…