BT composite that sequentially executes tasks until first [code]SUCCESS[/code]. BTSelector executes its child tasks sequentially, from first to last, until any child returns [code]SUCCESS[/code]. Returns [code]RUNNING[/code] if any child task returns [code]RUNNING[/code]. The composite will also remember the last child task that returned [code]RUNNING[/code], ensuring it resumes from that point in the next execution tick. Returns [code]FAILURE[/code] if all child tasks return [code]FAILURE[/code]. Returns [code]SUCCESS[/code] if a child task returns [code]SUCCESS[/code].