Issue Description:

It should be possible to mark some of our runtime functions with argmemonly readonly as they receive their type arguments indirectly via an array of type arguments.

I tried this in #14310 but tests failed. I did not have time to investigate why.

I mentioned that if that following situation in some form or another this annotation is not legal:

Type *args[5];
pointer->field = // inlined initialization
arg[1] = pointer
argmemonly(args)

However, we believe that this situation should? not arise. It might be worth investigating the failures.