Suppress timer.Dispose warnings in ETL base classes

Added pragma directives to suppress CA1849 and VSTHRD103 warnings
around timer.Dispose() calls in finally blocks of ExtractorBase,
LoaderBase, and TransformerBase. This clarifies that disposing the
timer without awaiting is intentional and correct in this context.

Author: Chris-Wolfgang

src/Wolfgang.Etl.Abstractions/ExtractorBase.cs

@@ -278,7 +278,9 @@ private async IAsyncEnumerable<TSource> ExtractWithProgressAsync(
         }
         finally
         {
+#pragma warning disable CA1849, VSTHRD103 // Timer.Dispose() is correct here; await is not valid in a finally block
             timer.Dispose();
+#pragma warning restore CA1849, VSTHRD103
             progress.Report(CreateProgressReport());
         }
     }

src/Wolfgang.Etl.Abstractions/LoaderBase.cs

@@ -280,7 +280,9 @@ private async Task LoadWithProgressAsync(
         }
         finally
         {
+#pragma warning disable CA1849, VSTHRD103 // Timer.Dispose() is correct here; await is not valid in a finally block
             timer.Dispose();
+#pragma warning restore CA1849, VSTHRD103
             progress.Report(CreateProgressReport());
         }
     }

src/Wolfgang.Etl.Abstractions/TransformerBase.cs

@@ -290,7 +290,9 @@ private async IAsyncEnumerable<TDestination> TransformWithProgressAsync(
         }
         finally
         {
+#pragma warning disable CA1849, VSTHRD103 // Timer.Dispose() is correct here; await is not valid in a finally block
             timer.Dispose();
+#pragma warning restore CA1849, VSTHRD103
             progress.Report(CreateProgressReport());
         }
     }