Support Multicall2 contract

[penandlim]

Changes in this PR

• Update the addresses to point to Multicall2
• Add another set of address map that contains Multicall2 addresses
• Add a new method Provider.tryAll which is identical to all except it will ignore any reverted calls (if any) and return null in place of their return values. This call relies on Multicall2 contract instances.
• Does not modify existing Provider.all function - it will still use the original Multicall contract instances.

TODO: deploy Multicall2 on chain 56
TODO: mark all read functions as view in ABI file Marked Multicall2.tryAggregate() function as view

Please double check the deployed contracts on sidechains match MakerDAO's repo and MakerDAO's deployment settings on eth mainnet!

Chain 56: https://bscscan.com/address/0x4c6bb7c24b6f3dfdfb548e54b7c5ea4cb52a0069#code
Chain 137: https://polygonscan.com/address/0xf43a7be1b284aa908cdfed8b3e286961956b4d2c#code

[Destiner]

@penandlim awesome, thanks a lot for this! Kudos for adding doc comments.

I would really love to merge this.

One concern I have is since this new multicall2 contract was deployed recently, it would be impossible to query historical data. Solution may be to keep using old Multicall for all call, and only use new Multicall for tryAll method.

[penandlim]

Hey @Destiner ! I've made the adjustment according to your comments. Let me know if this looks good!

[defidavid]

Can we get this merged up, @Destiner?

[Destiner]

Hey @penandlim and @DeFi-David. Sorry for a big delay, but I've just reviewed and merged it. Thanks again! I'm publishing this under beta tag, so if you want to install it, type npm install ethcall@beta.