parameters to use existing search, openai and storage account

[guyyardeni]

Motivation

Options to deploy the solution using an existing resource group, AI Search object, OpenAI object and storage account. This will save money and reduce object sprawl when multiple use cases are deployed.

Requirements

A list of requirements to consider this feature delivered
Deployment parameters to use existing copies of objects that support multiple AI use cases
Parameters should indicate that an existing object is to be used and then use the object name to indicate the existing object and skip creating a new object for those cases.

Thanks in advance.