Normalize '\r' in string literals to '\n'

<!--
Thank you for contributing to Ruff! To help us out with reviewing, please consider the following:

- Does this pull request include a summary of the change? (See below.)
- Does this pull request include a descriptive title?
- Does this pull request include references to any relevant issues?
-->

## Summary

This PR normalizes line endings inside of strings to `\n` as required by the printer.

<!-- What's the purpose of the change? What does it do, and why? -->

## Test Plan

I added a new test using `\r\n` and ran the ecosystem check. There are no remaining end of line panics. 


https://gist.github.com/MichaReiser/8f36b1391ca7b48475b3a4f592d74ff4

<!-- How was it tested? -->

crates/ruff_python_formatter/resources/test/fixtures/ruff/carriage_return/.editorconfig

@@ -0,0 +1,2 @@
+[*.py]
+end_of_line = crlf

crates/ruff_python_formatter/resources/test/fixtures/ruff/carriage_return/.gitattributes

@@ -0,0 +1 @@
+* text=auto eol=crlf

crates/ruff_python_formatter/resources/test/fixtures/ruff/carriage_return/string.py

@@ -0,0 +1,6 @@
+'This string will not include \
+backslashes or newline characters.'
+
+"""Multiline
+String \"
+"""