chore: Make Adapter an AbstractApiService #791

Job	Run time
lint	33s
javadoc	38s
units (17)	40s
units (11)	48s
units (8)	42s
dependencies (17)	47s
units (21)	51s
windows	1m 22s
clirr	29s
integration / integration-cassandra (11)	3m 9s
integration / integration-spanner (11)	6m 59s
	16m 58s

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