Logs keys order is non deterministic

[oshirohugo]

When using a hclog logger with json format in the plugin side and using json as format, the logs that will be output by the host will show the json keys in a non deterministic order.
For example, changing the Greet method from the basic example to:

func (g *GreeterHello) Greet() string {
	g.logger.Debug("message from GreeterHello.Greet")
	for i := 0; i < 50; i++ {
		g.logger.Debug("##msg from plugin##", "param1", 1, "param2", 2)
	}
	return "Hello!"
}

and running ./basic will show lines like:

2023-07-31T11:53:11.727+0200 [DEBUG] plugin.greeter: ##msg from plugin##: param1=1 param2=2 timestamp=2023-07-31T11:53:11.727+0200
2023-07-31T11:53:11.727+0200 [DEBUG] plugin.greeter: ##msg from plugin##: param2=2 param1=1 timestamp=2023-07-31T11:53:11.727+0200
2023-07-31T11:53:11.727+0200 [DEBUG] plugin.greeter: ##msg from plugin##: param1=1 param2=2 timestamp=2023-07-31T11:53:11.727+0200
2023-07-31T11:53:11.727+0200 [DEBUG] plugin.greeter: ##msg from plugin##: param2=2 param1=1 timestamp=2023-07-31T11:53:11.727+0200

where the order of the log keys is not preserved