ETH API: Remove message search from EthFeeHistory

[Stebalien]

Checklist

• This is not a new feature or an enhancement to the Filecoin protocol. If it is, please open an FIP issue.
• This is not a new feature request. If it is, please file a feature request instead.
• This is not brainstorming ideas. If you have an idea you'd like to discuss, please open a new discussion on the lotus forum and select the category as Ideas.
• I have a specific, actionable, and well motivated improvement to propose.

Lotus component

• lotus daemon - chain sync
• lotus miner - mining and block production
• lotus miner/worker - sealing
• lotus miner - proving(WindowPoSt)
• lotus miner/market - storage deal
• lotus miner/market - retrieval deal
• lotus miner/market - data transfer
• lotus client
• lotus JSON-RPC API
• lotus message management (mpool)
• Other

Improvement Suggestion

EthFeeHistory currently:

1. Loads all messages in a tipset.
2. Searches for the message receipts using StateSearchMsg.
3. Computes the "gas reward" from the message + receipt.

It also looks like it starts search at the current head.

This has a runtime of (height_scanned*messages_per_tipset)^2.

Given that we're walking backwards, we can instead:

1. Load the "parent receipts" from the current tipset.
2. Walk back one tipset.
3. Load the messages.
4. Use the receipts from step 1 and messages from step 3.
5. Repeat.