Maint: interface composition for HTTP proxy loop

- Change SetStatus to ApplyStatus
- Add Runner interface
- Add SettingsGetterSetter alias to state.SettingsGetterSetter

internal/httpproxy/run.go

@@ -7,6 +7,10 @@ import (
 	"github.com/qdm12/gluetun/internal/constants"
 )
 
+type Runner interface {
+	Run(ctx context.Context, done chan<- struct{})
+}
+
 func (l *looper) Run(ctx context.Context, done chan<- struct{}) {
 	defer close(done)