Extend CliUserConfig with the `logRetentionGB` setting to allow users to specify an upper limit to the total size of the logs directory in GB (float, can be less than 1, no default value). We will not set an individual limit to the size of log files since we want to retain the current behavior of a new log file per session. As sessions can produce varied sizes of log files, we want to enforce this by the total storage used by mongosh logs.

This `logRetentionGB` setting should work in combination with the `logRetentionDays` and `logMaxFileCount` setting. See tech design for more details.