Support wrapping within triply-quoted f-strings

[PeterJCLaw]

From what I can tell, it's not valid to have line breaks within a singly quoted f-string (i.e: f"foo {bar}") even if the line breaks appear within a substitution block. Triply quoted (i.e: traditional multi-line strings) do seem to support line breaks in substitution blocks:

f"""
  foo
  {bar(
    3,
  )}
"""

Following form this it might be nice if tuck supported wrapping in these cases. Maybe.

This would need to be a Python 3.12+ only feature though, since only 3.12+ offers useful tokens within f-strings. At that point we'll also need to rework some of our token parsing code given that we currently rely on token.string as a shorthand, however that's not always reliable (see e.g: PeterJCLaw/flake8-commas@8ee37e0).