Analyzer-specific properties in eng/Analyzer.props are evaluated before IsAnalyzerProject is set #15322

Issue description

Follow-up discovered while investigating #15314; separate from its architecture-routing fix.

Directory.Build.props imports eng/Analyzer.props before the project body is evaluated. eng/Analyzer.props defaults IsAnalyzerProject to false and immediately conditions a property group on it being true. However, the analyzer/code-fix projects declare <IsAnalyzerProject>true</IsAnalyzerProject> in their project bodies, after that import.

Consequently, the conditional group is skipped and is not reevaluated when the project later sets the property. Its intended settings do not take effect:

<PropertyGroup Condition="'$(IsAnalyzerProject)' == 'true'">
  <IsRoslynComponent>true</IsRoslynComponent>
  <DefineConstants>WINFORMS_ANALYZERS</DefineConstants>
</PropertyGroup>

This means the projects are marked as analyzer projects by the end of evaluation, but lack the intended Roslyn-component marker and compilation symbol. No additional runtime or packaging failure is claimed here; the confirmed defect is the missing evaluated properties.

Steps to reproduce

In a restored checkout, run:

dotnet msbuild src\System.Windows.Forms.Analyzers\src\System.Windows.Forms.Analyzers.csproj -getProperty:IsAnalyzerProject,IsRoslynComponent,DefineConstants -nologo

Observed:

{
  "Properties": {
    "IsAnalyzerProject": "true",
    "IsRoslynComponent": "",
    "DefineConstants": "TRACE;DEBUG"
  }
}

Expected: IsRoslynComponent=true, and DefineConstants includes WINFORMS_ANALYZERS while preserving existing symbols.

Suggested scope

Apply analyzer-dependent settings after the project has declared IsAnalyzerProject (for example, in the existing analyzer targets mechanism), preserving any existing compilation symbols. Add evaluation regression coverage for the C# and VB analyzer/code-fix projects, plus a non-analyzer control project.

.NET version

Reproduced with the repository-pinned SDK 12.0.100-alpha.1.26480.102 during investigation of #15314.

Did it work in .NET Framework?

Not applicable: repository MSBuild evaluation issue.

Did it work in any earlier release?

Not verified; this appears to predate the changes in #15314.