feat: Migrate to ethers v6

[perryrare]

Deps changes

• Removed 0xsequence/multicall, as JsonRpcProvider from ethers v6 provides the batch functionality
• Updated deps - hardhat, typechain, @typechain/hardhat to support ethers v6
• Removed ethereum-waffle and @nomiclabs/hardhat-waffle, as they are actually not used, and there isn't yet new versions of them supporting ethers v5
• Upgraded to ethers ^v6.6.2

Breaking changes

• LooksRare class now requires JsonRpcProvider (from ethers v6), instead of base provider as before.

...

• Updates tests. And they are passing ✅
• FYI, major version is not bumped in this PR. To keep supporting ethers v5, we will have to manage the updates in 2 different branches. (e.g. master and ethers-v5)