logging: Inline Caddyfile syntax for ip_mask filter

[francislavoie]

Just a small change to allow inlining the IP mask bits.

The config for IP masks is too verbose right now, especially because we log the IP in multiple fields: request>remote_ip, request>client_ip, and possibly in request headers depending on the clients/proxies.

Before:

			request>remote_ip ip_mask {
				ipv4 16
				ipv6 32
			}
			request>client_ip ip_mask {
				ipv4 16
				ipv6 32
			}

After:

			request>remote_ip ip_mask 16 32
			request>client_ip ip_mask 16 32