[Out-of-process-collection] Add releasing documentation for forwarder packages (open-telemetry#4373)

* Release CI + Instructions.

* run

* remove branch validation

* Remove Releasing Notes, will be added later in next PR.

* Restore releasing.md and remove yaml

Author: rajkumar-rangaraj

next-gen/RELEASING.md

@@ -0,0 +1,91 @@
+# Releasing OpenTelemetry.OutOfProcess.Forwarder Packages
+
+This document describes how to release the OpenTelemetry.OutOfProcess.Forwarder packages.
+
+## Overview
+
+The OpenTelemetry.OutOfProcess.Forwarder consists of two NuGet packages:
+- **OpenTelemetry.OutOfProcess.Forwarder** - Core forwarder functionality
+- **OpenTelemetry.OutOfProcess.Forwarder.Configuration** - Configuration extensions
+
+## Release Process
+
+### 1. Prepare for Release
+
+1. Ensure all changes are merged to the `out-of-process-collection` branch
+2. Update version numbers and changelog if needed
+3. Verify all tests are passing
+
+### 2. Build Release Packages
+
+1. Navigate to the repository's **Actions** tab
+2. Select the **release-nextgen-forwarder-packages** workflow
+3. Click **Run workflow**
+4. Fill in the required parameters:
+   - **Version**: Enter the release version (e.g., `1.0.0`, `1.0.0-alpha.1`, `1.0.0-beta.1`)
+   - Ensure you're running from the `out-of-process-collection` branch
+5. Click **Run workflow**
+
+### 3. Verify Build
+
+1. Wait for the workflow to complete successfully
+2. Check the workflow summary for:
+   - ✅ All tests passed
+   - ✅ Packages were built and validated
+   - ✅ Package sizes are reasonable
+   - ✅ Artifact was uploaded
+
+### 4. Download and Publish Packages
+
+1. From the completed workflow run, download the `opentelemetry-nextgen-forwarder-packages` artifact
+2. Extract the `.nupkg` files from the downloaded zip
+3. Verify the package contents if needed:
+   ```bash
+   dotnet validate package local OpenTelemetry.OutOfProcess.Forwarder.{version}.nupkg
+   dotnet validate package local OpenTelemetry.OutOfProcess.Forwarder.Configuration.{version}.nupkg
+   ```
+
+4. Publish to NuGet.org using your API key:
+   ```bash
+   dotnet nuget push OpenTelemetry.OutOfProcess.Forwarder.{version}.nupkg --api-key YOUR_API_KEY --source https://api.nuget.org/v3/index.json
+   dotnet nuget push OpenTelemetry.OutOfProcess.Forwarder.Configuration.{version}.nupkg --api-key YOUR_API_KEY --source https://api.nuget.org/v3/index.json
+   ```
+
+### 5. Verify Publication
+
+1. Check that packages appear on [nuget.org](https://www.nuget.org/packages?q=OpenTelemetry.OutOfProcess.Forwarder)
+2. Verify package metadata and dependencies are correct
+3. Test installation in a sample project:
+   ```bash
+   dotnet add package OpenTelemetry.OutOfProcess.Forwarder --version {version}
+   dotnet add package OpenTelemetry.OutOfProcess.Forwarder.Configuration --version {version}
+   ```
+
+## Versioning Guidelines
+
+- **Stable releases**: Use semantic versioning (e.g., `1.0.0`, `1.1.0`, `2.0.0`)
+- **Preview releases**: Use preview suffixes (e.g., `1.0.0-alpha.1`, `1.0.0-beta.1`, `1.0.0-rc.1`)
+- **Development builds**: Use preview suffixes with build numbers (e.g., `1.0.0-alpha.1.123`)
+
+## Troubleshooting
+
+### Build Failures
+- Check that all project references are valid
+- Ensure the `out-of-process-collection` branch is up to date
+- Verify that tests are passing locally
+
+### Package Validation Failures
+- Review package dependencies and target frameworks
+- Check for missing required metadata in `.csproj` files
+- Ensure package content is properly included
+
+### Publishing Failures
+- Verify NuGet API key is valid and has correct permissions
+- Check that package versions don't already exist (unless using `--skip-duplicate`)
+- Ensure package names match exactly
+
+## Related Documents
+
+- [Main Repository Releasing Guide](../docs/releasing.md)
+- [Package Configuration](src/OpenTelemetry.OutOfProcess.Forwarder/OpenTelemetry.OutOfProcess.Forwarder.csproj)
+- [Workflow Definition](../.github/workflows/release-nextgen-forwarder-packages.yml)