Switch PAT to GitHubApps

[chidozieononiwu]

This pull request introduces updates to the archetype-cpp-release.yml pipeline template to improve authentication and GitHub integration. The main changes focus on standardizing token usage and ensuring proper authentication for GitHub operations.

Authentication and GitHub Integration Updates:

• Added a step to log in to GitHub using the login-to-github.yml template, parameterized with TokenOwners for proper token scoping.
• Updated the authentication token used by the Add-IssueComment.ps1 script from $(azuresdk-github-pat) to $(GH_TOKEN) to align with the new login process.

cpp - template

Part of resolving Azure/azure-sdk-tools#9842

[Copilot]

Pull request overview

This PR updates the C++ release pipeline template to use GitHub App–minted tokens for GitHub operations, reducing reliance on the legacy PAT-based secret.

Changes:

• Adds the shared login-to-github.yml step to mint a GitHub App installation token scoped to $(VcpkgPrRepoOwner).
• Switches Add-IssueComment.ps1 authentication from $(azuresdk-github-pat) to $(GH_TOKEN).