SI-8608 f-interpolator inlines StringOps

Instead of "hi".format(), emit new _root_.s.c.i.StringOps("hi").format(),
to clarify intent and avoid picking up some other implicit enhancement.

A further optimization would be to use String.format directly when
that is possible.  The ticket says it is not possible for
```
f"${BigDecimal(3.4)}%e"
```