Upgrade xunit to v3

[ilonatommy]

We are using

aspnetcore/eng/Versions.props

Line 320 in e232d58

<XunitVersion>2.9.2</XunitVersion>

In our tests. One of the problems it creates is lack of failure when no tests were discovered. We could observe it in #62223.

We used a simple workaround for E2E tests that is checking logs for abnormal number of tests run: #62222.

A permanent workaround would be bumping xunit version, proposed in #62222 (comment).