Extend PackReference with locked and missing nodes

[brondani]

Fixes

• Protocol extensions supporting fixes for Manage Pack: Problem appears during pack development vscode-cmsis-solution#255

Checklist

• 🤖 This change is covered by unit tests (if applicable).
• 🤹 Manual testing has been performed (if necessary).
• 🛡️ Security impacts have been considered (if relevant).
• 📖 Documentation updates are complete (if required).
• 🧠 Third-party dependencies and TPIP updated (if required).