Create EventSource and EventSink handles #2752

Job	Run time
Benchmarks (hydra-node, tx-cost, --output-directory $(pwd)/../benchmarks)	4m 55s
Benchmarks (hydra-node, micro, -o $(pwd)/../benchmarks/ledger-bench.html)	4m 5s
Benchmarks (hydra-cluster, bench-e2e, datasets datasets/3-nodes.cbor datasets/1-node.cbor --outpu...	6m 3s
Build & test (plutus-cbor)	1m 25s
Benchmarks (plutus-merkle-tree, on-chain-cost, $(pwd)/../benchmarks)	1m 28s
Build & test (plutus-merkle-tree)	1m 21s
Build & test (hydra-plutus)	1m 18s
Build & test (hydra-tui)	4m 4s
Build haddock using nix	4m 43s
Build & test (hydra-node)	3m 57s
Build & test (hydra-cluster)	4m 14s
Build specification using nix	40s
Publish test results	0s
Documentation	0s
Publish benchmark results	0s
	38m 13s

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