Evaluate numerical field types

[jthreefoot-edb]

The schema has mostly tried to make sure the REST API output has accurate types instead of making every field a string like the output of barman diagnose. However, some are still strings instead of number or integer, such as max_replication_slots, max_wal_senders, and wal_keep_size (there may be others I've missed). Double check if these being strings is intentional or an oversight, and if necessary fix accordingly.