Add balancer vault artifact

[nlordell]

This PR refactors how the artifact vendoring works in order to add new Balancer Vault contract. In particular this PR:

• Strips even more JSON artifact properties that aren't used, namely:
  • contractName: the build script was overriding the contract name for all generated bindings
  • networks: they were being set for all contracts that we needed Contract::deployed() for (with the exception of WETH, but that was a very small amount of data to add).
  • bytecode: For contracts that are only needed as an interface and are not deployed for E2E
• Creates Sushiswap* to UniswapV2 symbolic links
  • This is done because they share an interface
  • The Sushiswap contracts weren't getting automatically vendored by the vendor.rs script.

Furthermore, two contracts for which we had bindings but are unused have been removed (UniswapV2Pair and SushiswapV2Pair, since we use IUniswapLikePair for both those contracts).

Test Plan

Added new tests to ensure that contracts have deployment information configured for all networks that we care about (to avoid another incident like we had in staging this morning).

Otherwise, no service changes, so CI will hopefully catch all issues.

[vkgnosis]

I was confused about contracts/artifacts/SushiswapV2Router02.json because the github diff renders this as if it c ontained the single line UniswapV2Router02.json. Actually it's a symbolic link to that file.

[nlordell]

I was confused about contracts/artifacts/SushiswapV2Router02.json because the github diff renders this as if it c ontained the single line UniswapV2Router02.json. Actually it's a symbolic link to that file.

Added info to the PR description

[bh2smith]

Really cool. Will look over the fact stuff again tomorrow morning.

[bh2smith]

One general comment, it looks like this kinda tooling could eventually fit more naturally in ethcontract. Given that it has become quite useful and sophisticated, it would be more easily accessible for other projects.

[nlordell]

looks like this kinda tooling could eventually fit more naturally in ethcontract

cowprotocol/ethcontract-rs#514

[fleupold]

nice, I wonder how we can encourage people to add tests here whenever a new contract is added.

[bh2smith]

Maybe we could somehow generate these lines from a constant list

include!(concat!(env!("OUT_DIR"), "/WETH9.rs"));

and include in this test and assertion each element from the list was verified here...

[nlordell]

#646