Replace base::lambda with shorter term.

base::lambda -> Fn (type alias for std::function).
base::lambda_once -> FnMut (type alias for base::unique_function).
base::lambda_guarded -> crl::guard.
base::lambda_call_type_t -> crl::deduced_call_type.

Telegram/SourceFiles/overview/overview_layout.cpp

@@ -83,7 +83,7 @@ public:
 private:
 	void startAnimation();
 
-	base::lambda<void()> _updateCallback;
+	Fn<void()> _updateCallback;
 	Ui::RoundCheckbox _check;
 
 	Animation _pression;