Failing tests: Tests referencing TestProject.ServiceA which isn't available on helix

## Summary

Multiple tests in the Aspire test suite are failing in the Azure DevOps CI environment due to missing test project files, specifically `TestProject.ServiceA.csproj`. These tests run on helix where the TestProject isn't available, so some project needs to be used.

## Build Information

- **Build ID**: 1160245
- **Pipeline**: 274 (Rolling build)
- **Date**: September 29, 2025
- **Build URL**:

## Error Details

**Error Message**:

```text
Aspire.Hosting.DistributedApplicationException : Project file 'D:\a\_work\1\s\tests\testproject\TestProject.ServiceA\TestProject.ServiceA.csproj' was not found.
```

## Affected Tests

The following test cases are failing with this error:

1. `Aspire.Hosting.Azure.Tests.AzureAppServiceTests.MultipleAzureAppServiceEnvironmentsSupported`
2. `Aspire.Hosting.Azure.Tests.AzureAppServiceTests.PublishAsAzureAppServiceWebsite_ThrowsIfNoEnvironment`
3. `KubernetesEnvironmentResourceTests.MultipleKubernetesEnvironmentsSupported`
4. `KubernetesEnvironmentResourceTests.PublishAsKubernetesService_ThrowsIfNoEnvironment`

## Impact

- **4 distinct test methods** failing
- **8 total test failures** (2 failures each)

Start with the four affected test methods in AzureAppServiceTests and KubernetesEnvironmentResourceTests, then inspect how they reference tests/testproject/TestProject.ServiceA/TestProject.ServiceA.csproj. Run the affected tests in the Helix configuration and update their project setup so the unavailable TestProject dependency is replaced appropriately. Done means all four methods pass in Azure DevOps CI without requiring TestProject.ServiceA.csproj.

Written by the indexing model from the issue text.