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

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 (https://github.com/Azure/azure-functions-dotnet-worker/pull/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.

Start by tracing the host-to-worker initialization flow and comparing it with the dotnet-isolated worker's host.json parsing described in the linked pull request. Identify which parsed values are in scope and where initialization data is exchanged; done means workers can receive those values without parsing host.json themselves.

Written by the indexing model from the issue text.