Add support for Azure Developer CLI

[tonybaloney]

• Adds a bicep validation workflow
• Changes the App Service deployment to compile on the server then uses a custom startup command to run the app (makes https://github.com/microsoft/azurechatgpt/blob/main/.github/workflows/open-ai-app.yml#L32C8-L54 redundant)
• Changes the scope of the bicep to resource group, so it can be used by users who aren't sub admins
• Provides default values to some of the parameters
• Makes some of the parameters runtime arguments so azd will prompt

This change probably breaks the "deploy to azure button" but that button doesn't support Bicep.

[tonybaloney]

Users will be prompted on the first turn

Then successive deployments will remember the settings