Initial Support for ARM in OpenAPI to TypeSpec Conversion

[joheredi]

This PR represents the initial effort to integrate ARM (Azure Resource Manager) support into the OpenAPI to TypeSpec plugin. Utilizing the @typespec/azure-resource-manager library, we now generate TypeSpec representations of Azure resources. A subsequent PR will address the definition of Resource operations.

Overview:

1. Consuming Resource Metadata (resources.json):

   • Originates from C# codegen efforts, reusing their discovery and metadata extraction processes.
   • A parallel project is ongoing to enhance C# codegen, aiming to output all necessary metadata for this feature.
   • Currently, the metadata is read from a JSON file located at the project root. Integration into the pipeline will be a focus of future work.

2. Per-Resource tsp File Generation:

   • Files generated will contain model declarations for both the Resources and their subsequent operations.
   • This is achieved using templates and decorators from @typespec/azure-resource-manager.

3. Reutilizing Data Plane Conversion Logic:

   • Efforts have been made to reuse existing components, including model generation, decorator logic, interfaces, and more.

Upcoming Work:

• Inclusion of Resource operations within the Resource file, utilizing templates from @typespec/azure-resource-manager.
• Removal of extraneous generated models.
• For ARM spec conversions, there won't be a need for the routes.tsp file, as operations are defined alongside the resources. However, this file remains relevant and necessary for data plane spec conversions.

[lirenhe]

As people are already using the converter for Swagger to TypeSpec conversion, let's try to merge this PR to avoid its growing larger and become more difficult to maintain. Thanks