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Add Minimal Implementation of MEV-Share SSE Collector

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Thought I'd get the ball rolling on this. Currently only added a collector following [https://docs.flashbots.net/flashbots-mev-share/searchers/event-stream](https://docs.flashbots.net/flashbots-mev-share/searchers/event-stream). I imagine eventually the MEV-Share implementation will have a complementary executor with shared types, so...