Add `[LiveTestOnly]` Test attribute to `Azure.Mcp.Tests`

[scbedd]

I have identified a couple packages that cannot migrate to recorded tests as they are not running on http.

• Some selected tests for speech work directly across websockets, which is not supported by the proxy as of this time: Migrate Azure.Mcp.Tools.Speech.LiveTests to recorded tests #1346
• Some tests for PostGres work directly on a tcp connection directly to the database. This is not http traffic.

We should provide an attribute that can run selected tests in recordings, and auto-skip the rest.