tests: add double OpenSession check in stress tests;

Author: LiamHamsters

src/Ydb.Sdk/src/Ado/Session/ImplicitSessionSource.cs

@@ -3,7 +3,7 @@ namespace Ydb.Sdk.Ado.Session;
 internal sealed class ImplicitSessionSource : ISessionSource
 {
     private readonly IDriver _driver;
-    private readonly ManualResetEventSlim _allReleased = new(false);
+    private readonly ManualResetEventSlim _allReleased = new(initialState: false);
     private int _isDisposed;
     private int _activeLeaseCount;
 

src/Ydb.Sdk/test/Ydb.Sdk.Ado.Tests/Session/YdbImplicitStressTests.cs

@@ -43,6 +43,9 @@ public async Task Dispose_WaitsForAllLeases_AndSignalsOnEmptyExactlyOnce()
 
                     s.Dispose();
                     closed.Inc();
+
+                    var s2 = await source.OpenSession(CancellationToken.None);
+                    s2.Dispose();
                 }
                 catch (ObjectDisposedException)
                 {
@@ -88,6 +91,9 @@ public async Task Stress_Counts_AreBalanced()
 
                     s.Dispose();
                     closed.Inc();
+
+                    var s2 = await source.OpenSession(CancellationToken.None);
+                    s2.Dispose();
                 }
                 catch (ObjectDisposedException)
                 {
@@ -118,6 +124,10 @@ public async Task Open_RacingWithDispose_StateRemainsConsistent()
             {
                 var s = await source.OpenSession(CancellationToken.None);
                 s.Dispose();
+
+                var s2 = await source.OpenSession(CancellationToken.None);
+                s2.Dispose();
+
                 return 1;
             }
             catch (ObjectDisposedException)