Implement performance metrics BehaveTree Node

[goudcode]

Description

I've implemented the performance per tree in the Godot engine profiler.
Time is being showed in nanosecconds and tree will be automatically added and removed to the profiler.

It might be better to disable all the metric code when running in release mode, example: use if OS.is_debug_build()
Any ideas are welcome.

Addressed issues

#89

Screenshots

[bitbrain]

Very good start! Apart from a few smaller comments this looks generally good.

Could we also add additional metrics like described on #89?

Metric Name	Description
beehave/node_count	The number of total beehave nodes in the scene
beehave/active_count	Number of active behaviour trees in the scene

Also reminder, that there is no need to check for debug mode, as Godot will only query the monitors inside the editor anyways and ensures not to call these in production mode.

[bitbrain]

we may want to give this a better name: as it is tracking the process_time of this tree, perhaps something like this:

Suggested change

	var _tree_metric_name : String
	var _process_time_metric_name : String

(we are inside the tree already so using "tree" is redundant)

[bitbrain]

From a structural perspective, we may want to have multiple metrics as part of the same tree. Therefore, I'd group them differently:

Suggested change

	_tree_metric_name = "beehave/process_time/%s(%s)" % [parent_name, get_instance_id()]
	_tree_metric_name = "beehave/%s-%s/process_time" % [parent_name, get_instance_id()]

[bitbrain]

Using get_parent() here is wrong, as there are different ways to associate a node to a tree (see actor_node_path export property)

Suggested change

	var parent_name = get_parent().name
	var parent_name = actor.name

[bitbrain]

Oh, this method also should be renamed to something like this:

Suggested change

	func _get_tree_metric() -> float:
	func _get_process_time_metric_value() -> float:

[goudcode]

The metric is now registered in the ready() function instead of the _enter_tree().
The reason for this is that the actor was not known in that function.

[bitbrain]

Thank you for your contribution!