🩹 [Docs]: Add suppressing output guidance to PowerShell style guidelines

[MariusStorhaug]

The PowerShell style guidelines now include comprehensive guidance on suppressing unwanted output from commands and methods. This addition helps developers choose the most performant approach when they need to discard function or method return values.

• Fixes [Docs]: Add suppressing output guidance to PowerShell style guidelines #224

Suppressing Output Section

A new section has been added to the PowerShell style guidelines (pwsh.instructions.md) that provides clear guidance on:

• Using $null = for best performance - The recommended approach for suppressing output from both cmdlets and .NET method calls
• Using [void] as an alternative - Another valid option specifically for method calls that return values
• Avoiding | Out-Null - Explicitly noting that this approach has significantly slower performance and should be avoided

The section includes practical examples showing both correct and incorrect usage patterns, making it easy for developers to follow the best practices.

Performance Impact

This guidance is especially important in performance-critical code and loops, where the overhead of | Out-Null can accumulate and cause noticeable slowdowns. By using $null = or [void], developers can ensure their scripts run efficiently.

[Copilot]

Pull Request Overview

This PR adds comprehensive guidance on suppressing unwanted output in PowerShell to the style guidelines. The addition addresses performance concerns by recommending the most efficient methods for discarding function and method return values.

• Added a new "Suppressing Output" section to the PowerShell style guidelines
• Provides clear recommendations for using $null = and [void] over | Out-Null
• Includes practical examples showing correct and incorrect usage patterns