Move worker.config.json to its own configuration source

A list of [WokerConfig](https://github.com/Azure/azure-functions-host/blob/dev/src/WebJobs.Script/Rpc/Configuration/WorkerConfig.cs) is created as part of the ScriptHost initialization. This is needed to index functions other than CSharp and to setup language worker processes.

Need to move the logic from ScriptHost InitializeAsync to new DI model