Add default firewall rule to allow netbird traffic (#1056)

Add a default firewall rule to allow netbird traffic to be handled 
by the access control managers.

Userspace manager behavior:
- When running on Windows, a default rule is add on Windows firewall
- For Linux, we are using one of the Kernel managers to add a single rule
- This PR doesn't handle macOS

Kernel manager behavior:
- For NFtables, if there is a filter table, an INPUT rule is added
- Iptables follows the previous flow if running on kernel mode. If running 
on userspace mode, it adds a single rule for INPUT and OUTPUT chains

A new checkerFW package has been introduced to consolidate checks across
route and access control managers.
It supports a new environment variable to skip nftables and allow iptables tests

client/internal/acl/manager_create.go

@@ -6,6 +6,8 @@ import (
 	"fmt"
 	"runtime"
 
+	log "github.com/sirupsen/logrus"
+
 	"github.com/netbirdio/netbird/client/firewall/uspfilter"
 )
 
@@ -17,6 +19,9 @@ func Create(iface IFaceMapper) (manager *DefaultManager, err error) {
 		if err != nil {
 			return nil, err
 		}
+		if err := fm.AllowNetbird(); err != nil {
+			log.Errorf("failed to allow netbird interface traffic: %v", err)
+		}
 		return newDefaultManager(fm), nil
 	}
 	return nil, fmt.Errorf("not implemented for this OS: %s", runtime.GOOS)