New signals, bug fixes and performance improvements

This release focuses on adding signals to Agent Behaviours and State Trees, fixing a number of bugs, and a couple of performance improvements:

Agent Behaviours

• The UtilityAIAgent has now the following new signals added: "behaviour_group_changed", "behaviour_group_exited", "behaviour_exited", "action_exited".
• The UtilityAIBehaviourGroup has now the signals: "behaviour_group_entered", "physics_frame_tick", "idle_frame_tick" and "behaviour_group_exited
• The UtilityAIBehaviour has now the signals: "behaviour_entered", "physics_frame_tick", "idle_frame_tick" and "behaviour_exited
• The UtilityAIAction has now the signals: "action_entered", "physics_frame_tick", "idle_frame_tick" and "action_exited
• Thank you to @Franz-Inc and @madeleineostoja for valuable feedback about the need for these signals.

State Tree

• The State Tree nodes gain the following signals: "state_check_enter_condition", "state_entered", "state_ticked" and "state_exited". These can be used instead extending the node with a script and defining the methods with similar names.

Behaviour Tree

• The CoolDownMSEC & USEC nodes were missing an initialization that caused a slight extra cooldown if the cooldown as triggered immediately at application start. That is now fixed.

Node Query System

• The Custom criterion had a bug where the defaults for is_filtered and score were not set, now that is corrected and they default to score=1.0 and is_filtered=false.
• After the time budgeting updates of the previous releases, the criterion score calculation had a bug that did not multiply the score correctly between criteria. That has now been fixed.
• Thanks to @Franz-Inc for pointing out these bugs!

General performance improvement

• In various places godot::Object::cast_to's have been replaced with cached pointers, which results in a performance boost.