Decouple extraneous dependencies and code from RestController

[seantleonard]

RestController is due for revisiting to clean up the code since it's been a few years.

• OpenApiDocumenter would benefit from its own Controller class to clean up the code.
• Special route handling can be added for Favicon.ico (or even just add favicon to the project)
• Cleanup DeterminePutPatchSemantics function which is currently multi purpose: reject etag usage and swap out operation types.
  • This should be split into two: middleware for rejecting etag usage (until we eventually support it), and just using expected operation types in restcontroller put patch routes.

[seantleonard]

working branch: https://github.com/Azure/data-api-builder/tree/dev/sean/restservice_cleanup