IR Building: Confusion in `FuncRef` ID
Currently when building a bundle through IR building API, for a function of Mu ID x, a MuFunction with x is created. Also a constant FuncRefpointing to the function is created, and the constant has its own ID as x. In a word, x is used for both for the function, and the constant. I am not sure if this is a typo or a deliberate decision. I assume that everything in Mu should have a unique ID, and using one ID for both a function and a funcref constant seems confusing. @u5211824