[ARC] Add support for wstETH on Arbitrum Aave V3

For clarification to the community regarding the pricing of wstETH on Arbitrum.

Currently, it is possible to price wstETH on Arbitrum composing 2 existing Chainlink price feeds: stETH/USD and wstETH/stETH. It is technically feasible to use that composed oracle with the parameters recommended, including the suggested eMode.

But with eModes including Liquidation Thresholds of the suggested levels (93%) and above, the problem described HERE becomes way more meaningful, as small deviations caused by de-synchronization carry higher risk.
In this specific case, given the deviation configurations of the 2 previous Chainlink feeds, the system should work correctly, as the risk added is not really high. But exists, so for the sake of its minimization, we have already contacted Lido and Chainlink to spin up a wstETH/ETH extra feed, in order to compose it with ETH/USD.
This way, ETH (price via ETH/USD) and wstETH (to be priced via ETH/USD + wstETH/ETH) will have almost perfect “sync” volatility-wise, with their common ETH/USD layer.




To summarise, eMode activation is legitimate and the oracle dependency should not be a blocker for it. We will help to spin up the right oracle adapter; depending on the availability of the new wstETH/ETH in any case, one or another composition.
Of course, if we would notice any non-expected risk, we would comment here on the forum if any post-Snapshot change in configs is required (always would be on the conservative direction).

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