chore: Use LF on all platforms (#3005)

I worked on #2993 and ran into issues that the formatter tests are failing on Windows because `writeln!` emits `\n` as line terminator on all platforms, but `git` on Windows converted the line endings in the snapshots to `\r\n`.

I then tried to replicate the issue on my Windows machine and was surprised that all linter snapshot tests are failing on my machine. I figured out after some time that it is due to my global git config keeping the input line endings rather than converting to `\r\n`. 

Luckily, I've been made aware of #2033 which introduced an "override" for the `assert_yaml_snapshot` macro that normalizes new lines, by splitting the formatted string using the platform-specific newline character. This is a clever approach and gives nice diffs for multiline fixes but makes assumptions about the setup contributors use and requires special care whenever we use line endings inside of tests. 

I recommend that we remove the special new line handling and use `.gitattributes` to enforce the use of `LF` on all platforms [guide](https://docs.github.com/en/get-started/getting-started-with-git/configuring-git-to-handle-line-endings). This gives us platform agnostic tests without having to worry about line endings in our tests or different git configurations.

## Note

It may be necessary for Windows contributors to run the following command to update the line endings of their files

```bash
git rm --cached -r .
git reset --hard
```

scripts/add_plugin.py

@@ -36,11 +36,12 @@ mod tests {
     use std::path::Path;
 
     use anyhow::Result;
+    use insta::assert_yaml_snapshot;
     use test_case::test_case;
 
     use crate::registry::Rule;
     use crate::test::test_path;
-    use crate::{assert_yaml_snapshot, settings};
+    use crate::settings;
 
     fn rules(rule_code: Rule, path: &Path) -> Result<()> {
         let snapshot = format!("{}_{}", rule_code.as_ref(), path.to_string_lossy());