feat: add `UnionExec` (#406) #276

Job	Run time
lint-and-test / Clippy	5m 39s
lint-and-test / Test Suite	21m 47s
lint-and-test / Format	14s
lint-and-test / Code Coverage	26m 19s
lint-and-test / Check Package	2m 42s
lint-and-test / Foundry project	6s
lint-and-test / solhint	9s
lint-and-test / Unused Dependencies	7m 10s
Release	6m 26s
	1h 10m 32s

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