Generated output (documentation, shell completion scripts, etc.) sometimes contain suboptimal whitespace

Generated output (documentation, shell completion scripts, etc.) sometimes contain suboptimal whitespace

**ArgumentParser version:** `main`
**Swift version:**

```text
swift-driver version: 1.120.5 Apple Swift version 6.1.2 (swiftlang-6.1.2.1.2 clang-1700.0.13.5)
Target: arm64-apple-macosx15.0
```

### Checklist

- [x] If possible, I've reproduced the issue using the `main` branch of this package
- [x] I've searched for [existing GitHub issues](https://github.com/apple/swift-argument-parser/issues)

### Steps to Reproduce

Search test comparison files in the various `Snapshots` folders to find trailing spaces, or multiple or no newlines at the end of the file.

Once fixed, the new `.editorconfig`s in the `Snapshot` folders can be removed.

### Expected behavior

No trailing spaces. One single newline at the end of every file.

### Actual behavior

Sometimes: trailing spaces, multiple newlines at the end of a file, or no newlines at the end of a file.

@rauhul

Search the test comparison files in the various Snapshots folders for trailing spaces and incorrect final newlines, then trace those outputs to their generators. Confirm generated documentation and shell completion scripts consistently have no trailing spaces and exactly one newline at EOF, and remove the new .editorconfig files from the Snapshot folders once fixed.

Written by the indexing model from the issue text.