Clean TestProgressState on TestExecutionCompleted by @Youssef1313 in #6505 (backport to rel/3.10) (#6551)

Co-authored-by: Youssef1313 <youssefvictor00@gmail.com>

Author: youssef-backport-bot

src/Platform/Microsoft.Testing.Platform/OutputDevice/Terminal/TerminalTestReporter.cs

@@ -159,6 +159,11 @@ public void TestExecutionCompleted(DateTimeOffset endTime)
         _terminalWithProgress.WriteToTerminal(_isDiscovery ? AppendTestDiscoverySummary : AppendTestRunSummary);
 
         NativeMethods.RestoreConsoleMode(_originalConsoleMode);
+
+        // This is relevant for HotReload scenarios. We want the next test sessions to start
+        // on a new TestProgressState
+        _testProgressState = null;
+
         _buildErrorsCount = 0;
         _testExecutionStartTime = null;
         _testExecutionEndTime = null;