Add option (-o/--output-file) to write output to a file (#4950)

## Summary

A new CLI option (`-o`/`--output-file`) to write output to a file
instead of stdout.

Major change is to remove the lock acquired on stdout. The argument is
that the output is buffered and thus the lock is acquired only when
writing a block (8kb). As per the benchmark below there is a slight
performance penalty.

Reference:
https://rustmagazine.org/issue-3/javascript-compiler/#printing-is-slow

## Benchmarks

_Output is truncated to only contain useful information:_

Command: `check --isolated --no-cache --select=ALL --show-source
./test-repos/cpython"`

Latest HEAD (361d45f2b2) with and without
the manual lock on stdout:

```console
Benchmark 1: With lock
  Time (mean ± σ):      5.687 s ±  0.075 s    [User: 17.110 s, System: 0.486 s]
  Range (min … max):    5.615 s …  5.860 s    10 runs

Benchmark 2: Without lock
  Time (mean ± σ):      5.719 s ±  0.064 s    [User: 17.095 s, System: 0.491 s]
  Range (min … max):    5.640 s …  5.865 s    10 runs

Summary
  (1) ran 1.01 ± 0.02 times faster than (2)
```

This PR:

```console
Benchmark 1: This PR
  Time (mean ± σ):      5.855 s ±  0.058 s    [User: 17.197 s, System: 0.491 s]
  Range (min … max):    5.786 s …  5.987 s    10 runs
 
Benchmark 2: Latest HEAD with lock
  Time (mean ± σ):      5.645 s ±  0.033 s    [User: 16.922 s, System: 0.495 s]
  Range (min … max):    5.600 s …  5.712 s    10 runs
 
Summary
  (2) ran 1.04 ± 0.01 times faster than (1)
```

## Test Plan

Run all of the commands which gives output with and without the
`--output-file=ruff.out` option:
* `--show-settings`
* `--show-files`
* `--show-fixes`
* `--diff`
* `--select=ALL`
* `--select=All --show-source`
* `--watch` (only stdout allowed)

resolves: #4754

crates/ruff_cli/src/lib.rs

@@ -1,3 +1,4 @@
+use std::fs::File;
 use std::io::{self, stdout, BufWriter, Write};
 use std::path::{Path, PathBuf};
 use std::process::ExitCode;
@@ -171,12 +172,26 @@ pub fn check(args: CheckArgs, log_level: LogLevel) -> Result<ExitStatus> {
         cli.stdin_filename.as_deref(),
     )?;
 
+    let mut writer: Box<dyn Write> = match cli.output_file {
+        Some(path) if !cli.watch => {
+            colored::control::set_override(false);
+            let file = File::create(path)?;
+            Box::new(BufWriter::new(file))
+        }
+        _ => Box::new(BufWriter::new(io::stdout())),
+    };
+
     if cli.show_settings {
-        commands::show_settings::show_settings(&cli.files, &pyproject_config, &overrides)?;
+        commands::show_settings::show_settings(
+            &cli.files,
+            &pyproject_config,
+            &overrides,
+            &mut writer,
+        )?;
         return Ok(ExitStatus::Success);
     }
     if cli.show_files {
-        commands::show_files::show_files(&cli.files, &pyproject_config, &overrides)?;
+        commands::show_files::show_files(&cli.files, &pyproject_config, &overrides, &mut writer)?;
         return Ok(ExitStatus::Success);
     }
 
@@ -276,7 +291,7 @@ pub fn check(args: CheckArgs, log_level: LogLevel) -> Result<ExitStatus> {
             noqa.into(),
             autofix,
         )?;
-        printer.write_continuously(&messages)?;
+        printer.write_continuously(&mut writer, &messages)?;
 
         // In watch mode, we may need to re-resolve the configuration.
         // TODO(charlie): Re-compute other derivative values, like the `printer`.
@@ -308,7 +323,7 @@ pub fn check(args: CheckArgs, log_level: LogLevel) -> Result<ExitStatus> {
                         noqa.into(),
                         autofix,
                     )?;
-                    printer.write_continuously(&messages)?;
+                    printer.write_continuously(&mut writer, &messages)?;
                 }
                 Err(err) => return Err(err.into()),
             }
@@ -341,10 +356,9 @@ pub fn check(args: CheckArgs, log_level: LogLevel) -> Result<ExitStatus> {
         // source code goes to stdout).
         if !(is_stdin && matches!(autofix, flags::FixMode::Apply | flags::FixMode::Diff)) {
             if cli.statistics {
-                printer.write_statistics(&diagnostics)?;
+                printer.write_statistics(&diagnostics, &mut writer)?;
             } else {
-                let mut stdout = BufWriter::new(io::stdout().lock());
-                printer.write_once(&diagnostics, &mut stdout)?;
+                printer.write_once(&diagnostics, &mut writer)?;
             }
         }