[new solver] Incorrect string escape of `{` as `\123` when stringleton returned from a type function

[deviaze]

Basically, when you have a type function that returns a stringleton (string singleton) which contains {, both hovers and TypeErrors containing that stringleton's value show \123 instead of {.

Repro: https://github.com/deviaze/solverbugs/blob/6f677813fd01716974f548d5da86c62de7c579e1/src/stringlefication.luau#L6

This may be a Luau Language Server issue instead of a Luau issue; lmk so I can move it there if it is.

[hgoldstein]

I think it's Luau side: I see the same thing in Studio.