OracleRouter Cleanup

[DanielVF]

We added a new OETHOracleRouter for the new launch. It is correct for OETH. We still have the old OracleRouter. However changes that were made in in the base code, make the non-eth router contract neither compatible with the current deployed OUSD code, nor correct for a new deploy of the new shared vault code for OUSD.
- We should move the price impl from OETHOracleRouter to OracleRouter
- We should get rid of the no longer needed price impl in OracleRouterBase and just have an empty method.

[DanielVF]

We may not need two separate oraclerouters. Might be a tiny bit more gas efferent to do so, but I think it's small.