Begin using `Mergeable` supplied by `dbt-common` #10169

Job	Run time
integration test metadata generation	1s
Test Log Schema (1)	3m 28s
Test Log Schema (2)	3m 20s
Test Log Schema (3)	3m 24s
Test Log Schema (4)	3m 48s
Test Log Schema (5)	3m 39s
Log Schema Test Suite	2s
	17m 42s

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