Add OpenTelemetry forwarder infrastructure (#9136)

* Add OpenTelemetry forwarder infrastructure

- Add OpenTelemetry.OutOfProcess.Forwarder.Configuration 0.1.0-beta.1 package version
- Add ENABLE_OTEL conditional compilation: when set, adds package reference and
  defines BUILDING_OTEL preprocessor symbol
- Set ENABLE_OTEL in generate-dev-sln.ps1 for dev builds
- Fix missing newline at end of generate-dev-sln.ps1

* Make OpenTelemetry package reference and BUILDING_OTEL unconditional

Address review feedback: remove ENABLE_OTEL gating so the package
is always referenced and BUILDING_OTEL is always defined, avoiding
the need for two separate builds.

* Remove BUILDING_OTEL define

Author: rajkumar-rangaraj

Directory.Packages.props

@@ -26,6 +26,7 @@
     <PackageVersion Include="Newtonsoft.Json" Version="$(NewtonsoftJsonVersion)" />
     <PackageVersion Include="NJsonSchema" Version="$(NJsonSchemaVersion)" />
     <PackageVersion Include="NJsonSchema.NewtonsoftJson" Version="$(NJsonSchemaVersion)" />
+    <PackageVersion Include="OpenTelemetry.OutOfProcess.Forwarder.Configuration" Version="0.1.0-beta.1" />
     <PackageVersion Include="System.CommandLine" Version="$(SystemCommandLineVersion)" />
     <PackageVersion Include="System.Private.Uri" Version="$(SystemPrivateUriVersion)" />
 

src/Tools/dotnet-monitor/dotnet-monitor.csproj

@@ -24,6 +24,7 @@
     <PackageReference Include="Microsoft.AspNetCore.Authentication.JwtBearer" />
     <PackageReference Include="Microsoft.AspNetCore.Authentication.Negotiate" />
     <PackageReference Include="Microsoft.Identity.Web" />
+    <PackageReference Include="OpenTelemetry.OutOfProcess.Forwarder.Configuration" />
     <PackageReference Include="System.CommandLine" />
     <PackageReference Include="Microsoft.AspNetCore.OpenApi" GeneratePathProperty="true" />
   </ItemGroup>