525 add helpers to allow configuration of services without the need of a host

[baseTwo]

Conceptual.

Thinking how we can open up the packaging tooling public. The idea is to wrap up the messy internals into something that hides this (and the IServiceProvider from the user)

Questions for the public facade

• Should we avoid asynchronous methods?
• Should we value ease of use higher than efficiency (e.g. string and byte[] over Streams)
• Is this one big API (cql ---> resources), or should each package have its own API

[baseTwo]

I've started with that a bit already in this PR, but the focus is first on getting the public API, and then fix the internals as it makes sense

Let's see if we can simplify AssemblyCompiler so that is more intuitively extensible and then we can fix the implementation. This will require a bit of design work.

[baseTwo]

BTW, I will still design a whole public facade around everything so that the user won't have to care about services and scopes. If we have a clean simple public facade, we can do a lot to clean up the internals more efficiently.

Regarding scopes, initially this was necessary to have for each libraryset (like a scope is maintained for each http request in asp.net). This is no longer needed, so that needs to be cleaned up too

Also, I don't this IAsyncEnumerable is the right strategy for processing elm into resource. I have some ideas around this