Fix SuppressMessage CustomRule by HeyItsGilbert · Pull Request #2142 · PowerShell/PSScriptAnalyzer

Problem: SuppressMessageAttribute failed when using named arguments for
RuleSuppressionID. Users could not use syntax like:
[SuppressMessage("RuleName", RuleSuppressionId="MyId")]

Root Cause: In RuleSuppression.cs, the named argument parser had two bugs:
1. Checked if RuleName was set instead of RuleSuppressionID
2. Assigned the value to RuleName instead of RuleSuppressionID

This broke selective rule suppression for custom rules.

Solution:
- Fixed conflict check to validate RuleSuppressionID instead of RuleName
- Fixed assignment to set RuleSuppressionID instead of RuleName
- Added comprehensive tests for named argument syntax
- Minor formatting improvements

Now both syntaxes work correctly:
[SuppressMessage("Rule", RuleSuppressionId="Id", Scope="Function")]
[SuppressMessage("Rule", "Id", Scope="Function")]

* Implemented a test case to validate the functionality of custom rules with targeted suppression.
* The test recreates the scenario from GitHub issue PowerShell#1686, ensuring that `RuleSuppressionID` works correctly with named arguments.
* Verified that violations are suppressed as expected based on the defined rules.