Have LookupSubjects return Unimplemented if a cursor is used #6633

Job	Run time
paths-filter	4s
Build Binary & Image	3m 39s
Analyzers Unit Tests	50s
Datastore Consistency Tests (crdb)	2m 3s
Datastore Integration Tests (crdb)	7m 41s
Datastore Consistency Tests (mysql)	2m 0s
E2E	2m 39s
Datastore Integration Tests (mysql)	2m 17s
Integration Tests	3m 56s
Datastore Consistency Tests (spanner)	3m 4s
Datastore Integration Tests (spanner)	1m 25s
Datastore Consistency Tests (postgres, 13.8)	2m 59s
Datastore Integration Tests (postgres, 13.8)	2m 41s
Datastore Consistency Tests (postgres, 14)	2m 50s
Datastore Integration Tests (postgres, 14)	2m 50s
Steelthread	2m 50s
Unit	6m 32s
Datastore Consistency Tests (postgres, 15)	3m 11s
Datastore Integration Tests (postgres, 15)	2m 24s
Datastore Consistency Tests (postgres, 16)	2m 48s
Datastore Integration Tests (postgres, 16)	2m 57s
Datastore Consistency Tests (postgres, 17)	2m 40s
WASM Tests	2m 7s
Datastore Integration Tests (postgres, 17)	2m 44s
Generate Protobufs	0s
Datastore Integration Tests (pgbouncer, 13.8)	3m 26s
Datastore Integration Tests (pgbouncer, 14)	3m 15s
Datastore Integration Tests (pgbouncer, 15)	3m 12s
Datastore Integration Tests (pgbouncer, 16)	3m 26s
Datastore Integration Tests (pgbouncer, 17)	2m 50s
	1h 25m 20s

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