Refactor in app HR handling

[dr1rrb]

✨ Feature

• Fix broken HR UI updates pausing
• Refactor UI update code to make it readable

What is the current behavior? 🤔

• UI pause is achieved using unrelated TypeMappings class
• Visual tree enumeration is achieved by calling unexpected ToArray

What is the new behavior? 🚀

• Dedicated class for UI pause, with explicit resume phase
• Use proper foreach

PR Checklist ✅

• [x] 📝 Commits must be following the Conventional Commits specification.
• [ ] 🧪 Added Runtime tests, UI tests, or a manual test sample for the changes have been added (for bug fixes / features) (if applicable)
• [ ] 📚 Docs have been added/updated which fit documentation template (for bug fixes / features)
• [ ] 🖼️ Validated PR Screenshots Compare Test Run results.
• [x] ❗ Contains NO breaking changes

[dr1rrb]

Note: This is a draft PR as the final goal is to split the "Dev Server client" from the "Hot Reload" logic as they are no longer deeply inter-dependent.

[unodevops]

🤖 Your Docs stage site is ready! Visit it here: https://unodocsprstaging.z13.web.core.windows.net/pr-22009/docs/index.html

[unodevops]

🤖 Your WebAssembly Skia Sample App stage site is ready! Visit it here: https://unowasmprstaging.z20.web.core.windows.net/pr-22009/wasm-skia-net9/index.html