src/vs/workbench/contrib/terminal/browser/terminalGroup.ts/TerminalGroup/setActiveInstanceByIndex
class TerminalGroup:	setActiveInstanceByIndex(index: number): void {
		// Check for invalid value
		if (index < 0 || index >= this._terminalInstances.length) {
			return;
		}

		const oldActiveGroup = this.activeInstance;
		this._activeInstanceIndex = index;
		if (oldActiveGroup !== this.activeInstance) {
			this._onInstancesChanged.fire();
			this._onDidChangeActiveInstance.fire(this.activeInstance);
		}
	}