Simplify baseline tests for RDG

Inspired by the conversation in https://github.com/dotnet/aspnetcore/pull/47741#discussion_r1177021092, now that we have more features in RDG we should consider implementing baseline tests that validate the code generated for more app like scenarios instead of single endpoints.

For example, instead of validating the baseline for a single parameter scenario like here:

https://github.com/dotnet/aspnetcore/blob/726f467f4c0d23b40a937edab56430c3861e73b9/src/Http/Http.Extensions/test/RequestDelegateGenerator/RequestDelegateCreationTests.Arrays.cs#L22-L41

We would check in baselines for more complex scenarios (like various combinations of parameters) as well as a single barebones scenario (to validate the unneeded type omission logic).