Mercury transmitter can use different codecs for native & link price reports

[martin-cll]

We are seeing the following error with a new v4 Mercury feed in staging testnet: failed to observe LINK price: failed to decode report: abi: improperly encoded uint32 value\nfailed to observe native price: failed to decode report: abi: improperly encoded uint32 value.

I believe this is caused by a v4 feed that uses a v3 native/link feedId:

• The native/link price is returned by the fetcher.LatestPrice here: https://github.com/smartcontractkit/chainlink/blob/develop/core/services/relay/evm/mercury/v4/data_source.go#L110-L149.
• I think, but I'm not 100% sure, that the fetcher is in fact a MercuryTransmitter: https://github.com/smartcontractkit/chainlink/blob/develop/core/services/relay/evm/mercury/transmitter.go#L497.
• The issue is that the mercury transmitter uses its internal codec to decode the link/native feed's reports so if the feed versions are different then it will get a decoding error which is what we are seeing in the logs.

The fix in this PR is to pass down a new BenchmarkPriceDecoder method that switches on the feedId to select the appropriate codec before decoding it for its benchmark price.

[samsondav]

This is implemented incorrectly

You’re supposed to create a different codec and pass that in

[cl-sonarqube-production]

Quality Gate passed

Issues
0 New issues
0 Fixed issues
0 Accepted issues

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0.0% Duplication on New Code

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