Consolidate the ABIU prompts in the CLI so it matches the UI behavior

[falahat]

Description

Today, ABIU and Runtime are two separate selections in the CLI.
This PR merges them into one selection. If you select an ABIU-enabled runtime, you automatically enable ABIU. If you want to disable ABIU, you can use the "nodejs" runtime

Scenarios Tested

• Created an ABIU backend runtime=nodejs22, it was marked as ABIU=enabled as expected
• Created a backend with runtime=nodejs noninteractively, it was marked as non-ABIU as expected
• Went through the interactive flow for backend creation and the prompt looked as expected. It correctly showed that nodejs would disable ABIU.

[gemini-code-assist]

Code Review

This pull request simplifies the App Hosting backend creation process by removing the explicit toggle for Automatic Base Image Updates (ABIU). ABIU support is now integrated into the runtime selection, where the promptRuntime utility displays whether a specific runtime supports the feature. As a result, the --automatic-base-image-updates and --no-automatic-base-image-updates flags, along with their associated prompts and logic, have been removed from the CLI and internal setup functions. I have no feedback to provide.