[Enhancement] Add a properties to configure max-archive-size option

Hi.
We have some big database to backup and we got some issue with ephemeral storage usage.
We was able to manage the useg setting max-archive-size, but to do so we have tu use the additionalCommandArgs property.

to polish the yaml would be great to have a property in [DataBackupConfiguration](https://github.com/cloudnative-pg/barman-cloud/blob/v0.4.0/pkg/api/config.go#L274) [¶](https://pkg.go.dev/github.com/cloudnative-pg/barman-cloud/pkg/api#DataBackupConfiguration) and some documentation line about Ephemeral storage consumption and parameters like "jobs".

Start with DataBackupConfiguration in pkg/api/config.go, then review the existing documentation around additionalCommandArgs, max-archive-size, ephemeral storage consumption, and jobs. Done means the configuration exposes max-archive-size directly and the related storage guidance is documented.

Written by the indexing model from the issue text.