Create CosmosDBScalerFactory implementation

[chiangvincent]

We are currently redesigning the scale controller to unify the duplicate scaling logic that resides in each of the extensions (CosmosDB, ServiceBus, EventHubs, Storage, etc.) and the scale controller. As a part of this redesign, scale controller will call into IScalerFactory implementations defined in each extension, which allows the scale controller to retrieve IScaleMonitor and ITargetScaler (if supported) from each extension. This PR builds on top of the TBS Cosmos PR here

Process:
Create ScaleFactoryImplementation
Generate local nuget packages with -scv3 suffix in the version
Load this local nuget package into scale controller v3
Test locally that client instantiation is successful.

Resources:
Azure Functions Scale Controller Redesign.docx
Azure Functions WebJobs SDK scaling changes.docx
WebJobsSDK that calls into each scale monitor
Code snippet in v3.x that uses scale factory implementation
CosmosDB bindings docs

Clarifications:

1. Is scaling not supported for functions using a different database for leases? (Do not see references to leaseDatabaseName in the original scale monitor)
2. Where is validation of the CosmosDBTriggerAttribute done?
3. Does the processor name = lease prefix? What if this value is not provided?
4. If lease container does not exist, we cannot make scaling decisions?

[mathewc]

Closing this old draft PR - looks like it's obsolete?