Update W605 to check in f-strings

[dhruvmanila]

W605 checks for invalid escape sequences in a string.

For f-strings, we'll be looking for the same in a FStringMiddle token which is the non-expression part of the f-string. The rule extracts the body part which excludes the quotes and also skips the validation if it's a raw string:

ruff/crates/ruff/src/rules/pycodestyle/rules/invalid_escape_sequence.rs

Lines 51 to 64 in a4a4616

	let text = locator.slice(range);
	// Determine whether the string is single- or triple-quoted.
	let Some(leading_quote) = leading_quote(text) else {
	return;
	};
	let Some(trailing_quote) = trailing_quote(text) else {
	return;
	};
	let body = &text[leading_quote.len()..text.len() - trailing_quote.len()];
	if leading_quote.contains(['r', 'R']) {
	return;
	}

The FStringMiddle token contains both the above information for free. We just need to check if the token is a FStringMiddle or a String.