Fix syntax error false positives for escapes and quotes in f-strings (#20867)

Summary
--

Fixes #20844 by refining the unsupported syntax error check for [PEP
701]
f-strings before Python 3.12 to allow backslash escapes and escaped
outer quotes
in the format spec part of f-strings. These are only disallowed within
the
f-string expression part on earlier versions. Using the examples from
the PR:

```pycon
>>> f"{1:\x64}"
'1'
>>> f"{1:\"d\"}"
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
ValueError: Invalid format specifier '"d"' for object of type 'int'
```

Note that the second case is a runtime error, but this is actually
avoidable if
you override `__format__`, so despite being pretty weird, this could
actually be
a valid use case.

```pycon
>>> class C:
...     def __format__(*args, **kwargs): return "<C>"
...
>>> f"{C():\"d\"}"
'<C>'
```

At first I thought narrowing the range we check to exclude the format
spec would
only work for escapes, but it turns out that cases like `f"{1:""}"` are
already
covered by an existing `ParseError`, so we can just narrow the range of
both our
escape and quote checks.

Our comment check also seems to be working correctly because it's based
on the
actual tokens. A case like
[this](https://play.ruff.rs/9f1c2ff2-cd8e-4ad7-9f40-56c0a524209f):

```python
f"""{1:# }"""
```

doesn't include a comment token, instead the `#` is part of an
`InterpolatedStringLiteralElement`.

Test Plan
--

New inline parser tests

[PEP 701]: https://peps.python.org/pep-0701/

crates/ruff_python_formatter/resources/test/fixtures/ruff/expression/fstring.py

@@ -706,8 +706,6 @@ f'{1:hy "user"}'
 f'{1: abcd "{1}" }'
 f'{1: abcd "{'aa'}" }'
 f'{1=: "abcd {'aa'}}'
-# FIXME(brent) This should not be a syntax error on output. The escaped quotes are in the format
-# spec, which is valid even before 3.12.
 f'{x:a{z:hy "user"}} \'\'\''
 
 # Changing the outer quotes is fine because the format-spec is in a nested expression.