[evm] Oracle precompile UX would be improved by update time information

[Unique-Divine]

Problem

"Why does the precompile only return the price without also including the timestamp at which the price was last updated? This info is usually very important for contracts as you would want to verify if the price is stale by checking the timestamp." - from @berndartmueller in Audit comment

Solution

Here are some common interfaces that are standard for many Ethereum developers:

• ChainLink - v0.8/.../AggregatorV3Interface.sol
• Pyth - pyth-sdk-solidity/IPyth.sol

The Oracle Module exposes all of this information, so we can implement both of these interfaces over time on Nibiru's Oracle.sol precompiled contract. Let's focus on the ChainLink one for now since that's been cited as a more common request and handle the Pyth interface as a separate ticket.

The Ask

• Expose timestamp information for the oracle exchange rate query. Completed by feat(oracle): Add new DatedExchangeRate query with block timestamp and block height #2097
• Implement the ChainLink interface on the oracle precompile using 8 decimals and setting the round ID as the block number for simplicity. You can import the interface as an npm dependency and write an "is" statement to guarantee compatibility for users that import the precompiled contract.

2024-11-08 - Note on User Expectations

I asked around to a few of the teams building apps on top of Nibiru, and all of them mentioned that they want to follow the conventions for constants that are seen on Ethereum.

1. Setting the decimals (uint8) to 8 in the ChainLink interface is the most common.
2. No one I spoke to uses getRoundData for historical data in their contracts. Everyone used the latestRoundData method and ignored the values for roundId and answeredInRound, paying attention only to timestamps and the data feed value (price).

• ETH / USD ChainLink Data Feed Contract: This resource is useful see what values are in the live contract under the "Read Contract" tab.
• ChainLink Data Feeds

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• Relevant State of the Codebase when this issue was created: 62d4b1a
• Originally posted by @Unique-Divine in https://github.com/code-423n4/2024-10-nibiru-zenith/pull/27#discussion_r1797466011