[Template] Figure out solution for Shared project being tied directly to ASP.NET Core shared framework

Today the Aspire shared project that gets added to all Aspire solutions and auto-referenced by Aspire service projects depends on ASP.NET Core. This leads to issues for service projects that aren't ASP.NET Core projects, e.g. Blazor WebAssembly projects, JSPS projects (SPA), Worker projects, etc.

We need to figure out what the story is for shared code in service projects that aren't ASP.NET Core projects.