use --report-azdo instead of Azure DevOps task PublishTestResults

[Bertk]

use --report-azdo (use Microsoft.Testing.Extensions.AzureDevOpsReport nuget package) instead of Azure DevOps task PublishTestResults@2

see https://devblogs.microsoft.com/dotnet/microsoft-testing-platform-reporting/

[Bertk]

There is a warning message in build log which has to be fixed as well.

##[warning Azure DevOps live publishing failed to create the test run. '<' is an invalid start of a value. Path: $ | LineNumber: 2 | BytePositionInLine: 0.

See closed issue Azure/azure-sdk-for-net#58171. Does not look like a VS2026 issue because this is not used in this context.

@Evangelink Is this a known issue? How can I fix it?

[Evangelink]

I'm looking into that now

[Evangelink]

Correction after tracing the pipeline configuration: the Basic header itself is not the demonstrated problem. This PR is a cross-repository build from Bertk/coverlet, and Azure Pipelines is withholding a usable job token from the fork build.

Please enable Make secrets available to builds of forks on the pipeline's pull request validation trigger. Your existing SYSTEM_ACCESSTOKEN: $(System.AccessToken) mapping can stay as-is.

The confusing JSON warning is still a TestFX bug, and I updated microsoft/testfx#10983 accordingly. Azure DevOps returns a 302 sign-in redirect for the unusable token; our HttpClient follows it to an HTML page and then tries to deserialize that page as JSON. We should disable authentication redirects and emit the same actionable fork-build guidance already used by Arcade's Azure DevOps tooling.