Optimizer: add simplification for the convert_escape_to_noescape instruction
Including the required bridging stuff.
%2 = thin_to_thick_function %1 to $() -> ()
%3 = convert_escape_to_noescape %2 : $() -> () to $@noescape () -> ()
->
%3 = thin_to_thick_function %1 to $@noescape () -> ()