fix: #2123 Logging of user defined firewall rules

fix: #2123 Logging of user defined firewall rules

This allows a user to log traffic filtered by a self defined firewall rule.
Therefore the API is extended to include a 'log' option allow to specify the
log level for each rule individually.

The 'log' option can also be specified in the fw config. In order to reduce the
log amount, logging is limited to 1 entry per second.

For now the rule has to be created or edited via the pvesh API call or via the
firewall config in order to set the log level.

Signed-off-by: Christian Ebner <c.ebner@proxmox.com>