feat(policy): limit/offset throughout LIST protos/gencode (#1668)

PR 1 related to #55 (must release `/protocol/go` to be able to consume
within `service` module).

Defaulting the limit value within the db package rather than the service
package to avoid setting a default that later requires changes within
the protos ([see best
practices](https://protobuf.dev/programming-guides/dos-donts/#change-default-value))
and to ensure consistency across policy objects.