Proj0025: Migrate from ruleset file to .globalconfig file

Microsoft deprecated the use of .ruleset in favor of .globalconfig files. In Visual Studio by clicking the file, it will automatically pop up a dialog to convert the ruleset.

Alternatively, you can download the converter yourself from NuGet. For more info: learn.microsoft.com

Note the difference between .editorconfig and .globalconfig here. It is advised to put analyzer configuration in the [.globalconfig file](https://learn.microsoft.com/dotnet/fundamentals/code-analysis/configuration-files#global-analyzerconfig).

Non-compliant

<Project Sdk="Microsoft.NET.Sdk">

  <PropertyGroup>
    <TargetFramework>net8.0</TargetFramework>
    <CodeAnalysisRuleSet>MyPreferences.ruleset</CodeAnalysisRuleSet>
  </PropertyGroup>

</Project>

Compliant

<Project Sdk="Microsoft.NET.Sdk">

  <PropertyGroup>
    <TargetFramework>net8.0</TargetFramework>
  </PropertyGroup>
    
</Project>

.globalconfig

is_global = true

dotnet_diagnostic.CA1000.severity = warning
...

or with an explicit import of a config file:

<Project Sdk="Microsoft.NET.Sdk">

  <PropertyGroup>
    <TargetFramework>net8.0</TargetFramework>
  </PropertyGroup>
  
  <ItemGroup Label="Analyzer configuration">
    <GlobalAnalyzerConfigFiles Include="analyzers-config.ini" />
  </ItemGroup>
  
</Project>