refactor(dbtest): Support new paths for migration files

This updates the docker image used for tests to support the new location
for sql migration files and the concept of editions. It continues to
process the old paths for now if the new directory does not exist, so
that the same image can be used during the transition.

testing/dbtest/docker/Makefile

@@ -36,7 +36,7 @@ database-up:
 		-e POSTGRES_DB=boundary \
 		-e PGDATA=/pgdata \
 		--mount type=tmpfs,destination=/pgdata \
-		-v "$(CWD)/../../../internal/db/schema/migrations/postgres":/migrations \
+		-v "$(CWD)/../../../internal/db/schema/migrations":/migrations \
 		$(IMAGE_TAG) \
 		-c 'config_file=/etc/postgresql/postgresql.conf' \
 		$(PG_OPTS) 1> /dev/null