Light Freshness Edit: ASP.NET - migration & tutorials

[lootle1]

This PR contains freshness updates to the following articles:

• Migrate from ASP.NET Core in .NET 8 to ASP.NET Core in .NET 9
• Get started with NSwag and ASP.NET Core
• Part 7, add a new field to a Razor Page in ASP.NET Core
• Tutorial: Call an ASP.NET Core web API with JavaScript

Minor grammar/style updates. Link updates.
For request details, see 568764

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Internal previews

📄 File	🔗 Preview link
aspnetcore/host-and-deploy/iis/index.md	Host ASP.NET Core on Windows with IIS
aspnetcore/migration/80-to-90.md	[Visual Studio](https://review.learn.microsoft.com/en-us/aspnet/core/migration/80-to-90?branch=pr-en-us-37114)
aspnetcore/tutorials/getting-started-with-NSwag.md	Get started with NSwag and ASP.NET Core
aspnetcore/tutorials/razor-pages/new-field.md	Part 7, add a new field to a Razor Page in ASP.NET Core
aspnetcore/tutorials/web-api-javascript.md	Tutorial: Call an ASP.NET Core web API with JavaScript

[wadepickett]

@lootle1, just in case, is this waiting for a review? It was still in draft so I had assumed not.

[lootle1]

@wadepickett not quite yet, it'll be finished by tomorrow and will tag you here once it's ready. Thank you :)

[MeeraDi]

Replaced by #37136