Update ASP.NET Core integration testing article to be based on Blazor

### Description

The ASP.NET Core integration testing article is currently based on Razor Pages. We should update it to be based on Blazor and to address Blazor-related integration testing concerns specific to its various render modes.

The article recommends Playwright for testing SPAs, but this guidance presumably applies to testing Blazor apps as well that have client-side rendering logic..

### Page URL

https://learn.microsoft.com/en-us/aspnet/core/test/integration-tests?view=aspnetcore-9.0

### Content source URL

https://github.com/dotnet/AspNetCore.Docs/blob/main/aspnetcore/test/integration-tests.md

### Document ID

f499b131-8b14-7e10-1728-543fdd5a5656

### Platform Id

a725fe2a-b11f-6664-eb77-2adc94d55792

### Article author

@tdykstra

### Metadata

* ID: 77889d43-fedb-f8b4-8fea-379ec946555c
* PlatformId: a725fe2a-b11f-6664-eb77-2adc94d55792
* Service: **aspnet-core**
* Sub-service: **testing**

[Related Issues](https://github.com/dotnet/AspNetCore.Docs/issues?q=is%3Aissue+is%3Aopen+f499b131-8b14-7e10-1728-543fdd5a5656)