fix(fast-element): avoid mutating render template bindings

[janechu]

Pull Request

📖 Description

• Avoid mutating caller-owned template Binding instances passed to render().
• Preserve string, node, and template resolution by adapting the binding used internally by the render directive.
• Add regression coverage for reusing the same template binding across different render data bindings.

👩‍💻 Reviewer Notes

Please focus review on the render() template binding adapter behavior.

📑 Test Plan

• npx biome check packages\fast-element\src\templating\render.ts packages\fast-element\src\templating\render-binding.pw.spec.ts change\@microsoft-fast-element-2613f3cc-434d-4262-96ad-f1ab70e28a86.json
• npm run build:tsc -w @microsoft/fast-element && npm run build:rollup -w @microsoft/fast-element && npm run build:sizes -w @microsoft/fast-element
• npx playwright test --project=chromium -g "does not mutate a provided template binding" from packages\fast-element
• npx playwright test --project=chromium -g "The render" from packages\fast-element
• npx beachball check --branch origin/releases/fast-element-v3 --scope "!sites/*" --changehint "Run 'npm run change' to generate a change file"

✅ Checklist

General

• I have included a change request file using $ npm run change
• I have added tests for my changes.
• I have tested my changes.
• I have updated the project documentation to reflect my changes.
• I have read the CONTRIBUTING documentation and followed the standards for this project.