Update Aspire integration documentation

[davidfowl]

Integrations are the term used to describe both hosting and library integrations.

Hosting integrations exist to provide configuration for the application. These packages provide configuration by provisioning resources (such as containers, or cloud resources) or pointing at existing ones (a local SQL server for example). This configuration is usually consumed by a client/libary integration package that understands this configuration schema.

Client/Library integrations define configuration schema, wire up client libraries to DI, add health checks, resiliency and telemetry.

Hosting and client/library integrations are best when used together, but are NOT coupled and may be used separately (some hosting integrations may not have a library integration for e.g.). Configuration is what makes the hosting integration work with the client library integration.

We should refocus the apphost overview on the core building blocks (what is there already) and how the orchestration model works (pointing to other articles like networking and parameters). We should move the list of packages and move them to the integrations page.

We should also move Dapr and Orleans under integrations and delete the frameworks node.

Under the extensibility node:

Creating custom integrations should be top level, and below it should be "hosting integration" and "library integration".

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Associated WorkItem - 310941