SI-8148 fix anonymous functions with placeholders in quasiquotes

Quasiquotes used to fail to generate proper fresh identifiers for
anonymous functions like:

```
  q"_ + _" // used to be parsed as q"(x$1, x$1) => x$1 + x$1"
```

Due to improper initialization of FreshNameCreator in quasiquote
parser which was erroneously not preserved throughout parsing of
the code snippet but re-created on every invocation.

review @retronym