Add C# analyzer for endpoint parameter

There was guidance that endpoint should be:
- A client parameter called “endpoint”
- Of type Uri (e.g. System.Uri) as per the [guidelines](https://azure.github.io/azure-sdk/dotnet_introduction.html#dotnet-primitives-uri)

There are some SDKs which generate endpoint as string([here](https://github.com/Azure/azure-sdk-for-net/blob/949c498f8abf925b4d8594e91c671ad3d64e4df8/sdk/deviceupdate/Azure.IoT.DeviceUpdate/src/Generated/DeviceUpdateClient.cs#L43) is one example). We can add an analyzer like: "If a client level path parameter is used in a parametrized host, then it must be called "endpoint" and it must be typed "format: url".