Prebuild language runtime images

[shibayan]

Summary

• add Ubuntu 24.04 prebuild definitions for all supported language runtimes
• publish AMD64 and ARM64 images to GHCR with rolling, dated, and revision tags
• update every template to use the corresponding prebuilt runtime image
• keep Azure Functions Core Tools selectable as a container Feature
• build pending prebuild definitions during pull request smoke tests
• verify all required multi-architecture images before publishing templates

Why

Installing language runtimes as Features during the first container startup is slow, especially for Python. Prebuilding every supported language provides consistent startup behavior and leaves a common place for future runtime customization.

Impact

The workflow publishes 21 runtime configurations for both supported architectures. Template patch versions are incremented, and smoke test failures now fail the pull request check.

Validation

• parsed all template and prebuild JSON files
• verified the generated prebuild matrix contains 21 runtime configurations
• checked all template image references and runtime Feature removals
• ran git diff --check

Full image builds require the GitHub Actions runners and will be validated by the pull request checks.