Remove a need for --config-on-postgres-host

[choplin]

Description

schema-importer provides a --config-on-postgres-host option for users to specify a config path that is accessible from the analytics PostgreSQL. This option is necessary because it is possible that we need to specify the different hostnames in the ScalarDB config properties between the local execution of schema-importer and the read of foreign tables in Postgres.

However, it would be difficult for users to properly understand how to set the configuration and command line options, especially what should be set to --config and --config-on-postgres-host.

Approach

It is theoretically possible that users need to specify the different hostnames in the ScalarDB config properties, but practically, we might be able to assume that users could access the hosts with the same hostnames from the local (i.e., where schema-importer is executed) and Postgres. If this is true, we can simply delete --config-on--postgres-host and use the same value for the schema-importer execution and the Postgres FDW configuration.

A known possible situation we would like to set different hostnames is local development using docker-compose. From, Postgres, the services are accessible with the service name specified in the docker-compose.yaml, but from schema-importer, we normally access the service as the localhost and the port forwarded from the container. If we will go the way mentioned above, we should care about this use case.