Add stateful pretty printer for references in REPL

When using the repl References are printed as ``
```
> val a = Ref 0;
val a = : int ref
```
Current implementation is here https://github.com/CakeML/cakeml/blob/5204d423c1b89d92a970f41f52da476d6cfb1e47/basis/pure/mlprettyprinterScript.sml#L217-L219
This should be what's printed instead
```
> val a = Ref 0;
val a = Ref 0: int ref
```

Start at basis/pure/mlprettyprinterScript.sml lines 217-219 and reproduce the REPL example from the issue. Trace how the reference value is printed, then verify that the REPL output shows Ref 0 while retaining the int ref type annotation.】【。

Written by the indexing model from the issue text.