R1:d8f51dff6ec3

Use the configured viewer more consistently in the Herald commit adapter

Summary: See PHI276. Ref T13048. The fix in D18933 got one callsite, but missed the one in the `callConduit()` method, so the issue isn't fully fixed in production. Convert this adapter to use a real viewer (if one is available) more thoroughly.

Test Plan: Ran rules in test console, saw field values. Will test in production again.

Reviewers: amckinley

Reviewed By: amckinley

Maniphest Tasks: T13048

Differential Revision: https…