feat: integrate ERC-4906

[PaulRBerg]

Closes #549 by integrating OpenZeppelin's IERC4906.

Function	Event
cancel	MetadataUpdate
renounce	MetadataUpdate
setNFTDescriptor	BatchMetadataUpdate
withdraw	MetadataUpdate

Notes:

• The rationale for emitting the MetadataUpdate event on every withdraw is thus: the state of the stream may change between withdrawals. We want to intercept every state-changing operation to make NFT marketplaces refresh our NFT SVGs.
  • Through this lens, we make the protocol users pay the cost of refreshing the NFT metadata - which is a fair requirement given that it plays to their advantage for the NFT SVG to be kept up to date.
• The same rationale applies to renounce
• I know that the _toTokenId passed to BatchMetadataUpdate is 0 when _nextStreamId is 1, but this should be a minor detail. I mean, one would hope that the _nextStreamId will not retain the value of 1 for long. Even in the worst-case scenario when this is a problem for NFT marketplaces, we can create a stream ourselves before calling setNFTDescriptor.

[tibbarytsur]

This mostly solves the problem except for the streamed amount/percentage between withdrawals. But I suppose the only way to handle that is the bot to trigger the relevant 3rd party APIs.

[PaulRBerg]

@andreivladbrg is this PR ready to be merged now?