SI-8148 fix anonymous functions with placeholders

Quasiquotes used to fail to generate proper fresh identifiers for
anonymous functions like:

  q"_ + _"

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.
Merge pull request #3372 from densh/si/8148

 fix anonymous functions with placeholders in quasiquotes