Refactor stream fetching in the SDK [SBK-347]

[alexisnsns]

When calling onAllStreams, fetching the streams (using streammanager.publicClient.getContractEvents) can be slow on public nets if you don't pass a 'fromBlock' param to start fetching only from a certain block.

The way we fetch the past streams can be improved.

• There's a linear increment in how the stream works, so you could just iterate them in batches using multicall for speed
• We can add a native multicall-like search for live streams into the contract (maybe query 256 at a time)
• Use the Graph?