Enable EnablePackageValidation for all src packages with 1.0.0 baseline (#1330)

Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>
Co-authored-by: jeffhandley <1031940+jeffhandley@users.noreply.github.com>
Co-authored-by: Stephen Toub <stoub@microsoft.com>
Co-authored-by: stephentoub <2642209+stephentoub@users.noreply.github.com>

Author: 3 people

src/Directory.Build.props

@@ -16,6 +16,8 @@
     <EmbedUntrackedSources>true</EmbedUntrackedSources>
     <AssemblyOriginatorKeyFile>$(RepoRoot)\Open.snk</AssemblyOriginatorKeyFile>
     <SignAssembly>true</SignAssembly>
+    <EnablePackageValidation>true</EnablePackageValidation>
+    <PackageValidationBaselineVersion>1.0.0</PackageValidationBaselineVersion>
   </PropertyGroup>
 
   <ItemGroup>