This is the core PR adding Blazor server and client nuget packages. Reworked samples using these packages will be merged separately, to keep this PR manageable.

The main idea is to combine the two approaches we've used historically: when using wasm, we need a BFF; when using blazor server, we need a server side (non http context based) token store. We use the existing bff server side session, and wire that into everything so that we can manage a consistent set of tokens regardless of the render context.

We also have helpers to create http clients that are appropriate for both blazor server and wasm. On blazor server, we retrieve the access token and use it. On wasm, we proxy the request through the bff. From the point of view of the component or service running in the blazor application, you just use an http client.