fix: Allow cloudflared ICMP proxy feature (#165)

When starting the cloudflared pod, the following is warning appears in
the logs:

```text
WRN The user running cloudflared process has a GID (group ID) that is not within ping_group_range. You might need to add that user to a group within that range, or instead update the range to encompass a group the user is already in by modifying /proc/sys/net/ipv4/ping_group_range. Otherwise cloudflared will not be able to ping this network error="Group ID 0 is not between ping group 1 to 0"
WRN ICMP proxy feature is disabled error="cannot create ICMPv4 proxy: Group ID 0 is not between ping group 1 to 0 nor ICMPv6 proxy: socket: permission denied"
```

Added the needed sysctl settings to the security context to enable this
feature and confirmed that the warning is removed.

cloudflare/cloudflared#1109

internal/controller/gateway_controller.go

@@ -599,6 +599,12 @@ func (r *GatewayReconciler) deploymentForGateway(
 						SeccompProfile: &corev1.SeccompProfile{
 							Type: corev1.SeccompProfileTypeRuntimeDefault,
 						},
+						Sysctls: []corev1.Sysctl{
+							{
+								Name:  "net.ipv4.ping_group_range",
+								Value: "0 0",
+							},
+						},
 					},
 					Containers: []corev1.Container{{
 						Image:           image,