Upgrade to latest graphrag library release

[jgbradley1]

This PR is currently in progress. The intent is to upgrade the codebase to use the latest release of the graphrag library, as well as make some additional refactoring changes to simplify the code and improve readability.

The following list of changes in this PR will be updated as they are made:

Bicep Updates:

• refactored the bicep code to be more generic and readable
• consolidated all RBAC role assignments into separate bicep files under /infra/core/rbac/* to help clarify what RBAC roles are required in case manual application of RBAC roles is needed. RBAC role assignments are made to the AKS workload identity and the AKS service itself.
• moved the logic of creating graphrag-specific cosmosdb databases/containers from bicep and into the backend docker image for better portability
• fixed an RBAC deployment issue that would cause sporadic deployment failures. When using guid() to name RBAC role assignments, there must be enough information passed to guid() to ensure global uniqueness. Otherwise this can result in a deployment failure.

Web App Updates - the backend graphrag API server

• refactored the file structure under backend/src such that the web API code is separate from other code
• refactored and cleaned up logging code to be simpler
• updated the auto-prompt tuning API endpoint to return prompts as a json response instead of a zip file
• updated all code references and pytests to use v1.2.0 of the graphrag library
• updated the web app code to hook into the graphrag library using the librarys' API layer - this allowed for the removal of a lot of redundant code
• updated pyproject.toml to use newer versions of python library dependencies

CI/CD Updates

• updated dependabot settings