1) Remove [EventSourceAutoGenerate], we rely on just [EventSource] + no explicit ctors

2) Introduce a new global SourceGenerators - EventSourceGenerator (and move the existing impl from SPC.Generators to this new project)
3) Update slnx files (via the UpdateSolutionFiles task)
4) Migrate all classes with [EventSource] to use the SG. Except for the ones with EtwSelfDescribingEventFormat

Author: EgorBo

src/libraries/System.Private.CoreLib/gen/EventSourceGenerator.csproj

@@ -0,0 +1,22 @@
+<Project Sdk="Microsoft.NET.Sdk">
+  <PropertyGroup>
+    <TargetFramework>netstandard2.0</TargetFramework>
+    <NoWarn>$(NoWarn);CS3001</NoWarn>
+    <IsRoslynComponent>true</IsRoslynComponent>
+  </PropertyGroup>
+  <PropertyGroup>
+    <DefineConstants Condition="'$(DotNetFinalVersionKind)' != ''">$(DefineConstants);STABILIZE_PACKAGE_VERSION</DefineConstants>
+  </PropertyGroup>
+
+  <ItemGroup>
+    <Compile Include="EventSourceGenerator.cs" />
+    <Compile Include="EventSourceGenerator.Emitter.cs" />
+    <Compile Include="EventSourceGenerator.Parser.cs" />
+    <Compile Include="$(CoreLibSharedDir)\System\Runtime\CompilerServices\IsExternalInit.cs" Link="Common\System\Runtime\CompilerServices\IsExternalInit.cs" />
+  </ItemGroup>
+
+  <ItemGroup>
+    <PackageReference Include="Microsoft.CodeAnalysis.CSharp" PrivateAssets="all" Version="$(MicrosoftCodeAnalysisVersion_LatestVS)" />
+  </ItemGroup>
+
+</Project>