Add API baseline files in Identity.UI and Authentication.*.UI projects

[dougbu]

After #24347, the following projects still lack API baseline files

• Microsoft.AspNetCore.Authentication.AzureAD.UI
• Microsoft.AspNetCore.Authentication.AzureADB2C.UI
• Microsoft.AspNetCore.Identity.UI

@pranavkm's #25736 worked around dotnet/roslyn#47350, removing the last obstacle to having public API throughout this repo. Filling this gap will also allow us to remove the first part of the Condition at https://github.com/dotnet/aspnetcore/blob/master/eng/targets/CSharp.Common.targets#L21-L24

We may need different clauses to avoid errors building analyzer projects, msbuild tasks, and similar projects.

[dougbu]

@Pilchie should I target 5.0.1 for fixing this issue❔

[dougbu]

Fixed in 4158756 / #27653