Implement --show-version-specifiers for tool list (#7050)

## Summary

Closes #6747 .

## Test Plan

```
cargo test --test tool_list
```

docs/reference/cli.md

@@ -3141,6 +3141,8 @@ uv tool list [OPTIONS]
 
 </dd><dt><code>--show-paths</code></dt><dd><p>Whether to display the path to each tool environment and installed executable</p>
 
+</dd><dt><code>--show-version-specifiers</code></dt><dd><p>Whether to display the version specifier(s) used to install each tool</p>
+
 </dd><dt><code>--verbose</code>, <code>-v</code></dt><dd><p>Use verbose output.</p>
 
 <p>You can configure fine-grained logging using the <code>RUST_LOG</code> environment variable. (&lt;https://docs.rs/tracing-subscriber/latest/tracing_subscriber/filter/struct.EnvFilter.html#directives&gt;)</p>