fix(og): L-02 - Emit event on syncing upgraded OOv3

[Reinis-FRP]

Motivation

OZ identified the following issue:

The internal _sync function changes the OptimisticOracleV3 contract used by the
OptimisticGovernor , but unlike other administrative setter functions, it does not emit an
event when a change occurs.

Summary

This PR addresses this issue by adding a new OptimisticOracleChanged event that is emitted by _sync whenever the finder contract returns a different address than that of the current optimisticOracleV3 variable.

Testing

Check a box to describe how you tested these changes and list the steps for reviewers to test.

• Ran end-to-end test, running the code as in production
• New unit tests created
• Existing tests adequate, no new tests required
• All existing tests pass
• Untested

[chrismaree]

this seems a bit counter intuitive to emit the currentOptimisticOracleV3 over the optimisticOracleV3. would you not want to emit the value of the new oov3?

[Reinis-FRP]

Agree, fixed in 3ee4250 by renaming currentOptimisticOracleV3 to newOptimisticOracleV3.

[mrice32]

LGTM!