CosmosDB add option for Autoscale throughput

[viktorvan]

First off, I am aware of the issue for serverless throughput #333 but that issue is on hold until the serverless feature leaves preview.

In addition to the manual throughput for CosmosDB there's also the Autoscale option.

The ARM schema looks like this:

"options": {
      "throughput": "integer",
      "autoscaleSettings": {
        "maxThroughput": "integer"
      }
    }

I would propose that we add a Throughput type:

type Throughput =
    | Manual of int<CosmosDb.RU>
    | Autoscale of int<CosmosDb.RU>

I am using this feature now, so I would be happy to have it included in Farmer, and wouldn't mind helping out with the implementation.

This issue may also be related to #337 since autoscale throughput can be set on the database as well as on the container level.