[Analyzer] Warn about returning `IEnumerable<T>` from action or minimal API

### Is there an existing issue for this?

- [X] I have searched the existing issues

### Is your feature request related to a problem? Please describe the problem.

> Returning `IEnumerable` from an action results in synchronous collection iteration by the serializer. The result is the blocking of calls and a potential for thread pool starvation. To avoid synchronous enumeration, use ToListAsync before returning the enumerable.

See https://learn.microsoft.com/en-us/aspnet/core/performance/performance-best-practices?view=aspnetcore-6.0#return-ienumerablet-or-iasyncenumerablet

### Describe the solution you'd like

An analyzer that warns when `IEnumerable` is returned from a controller or minimal API.

### Additional context

_No response_