Send (some?) parsed host.json values to worker during initialization

[brettsam]

Currently, some of the workers (notably dotnet-isolated) do their own parsing of host.json to pull in values that they need. The biggest one at the moment is the http routeprefix, which is used to provide route details to functions (Azure/azure-functions-dotnet-worker#1596).

However, this is unnecessary parsing on the worker side that can introduce other complexities (like differences in parsing behavior).

We need a way for the host to send some host.json details along to the worker as part of the worker initialization flow.

[jviau]

Can we clarify this as sending some configuration, not specifically host.json values to the worker