Fix Couchbase flaky tests (#6892)

## Summary of changes

The CouchBase and CouchBase3 tests are failing rarely in the CI due to
authentication errors. All of them seem to be due to Authorization
issues, not related to our instrumentation. That's why it has been
decided to skip these results when the flakiness occurs.

In the case of the CouchBase tests, we are getting these stacktraces
depending on the package version:

```
Unhandled exception. System.AggregateException: Could not bootstrap - check inner exceptions for details. (One or more errors occurred. (Authentication failed for bucket 'default')) (Cannot deserialize the current JSON array (e.g. [1,2,3]) into type 'Couchbase.Configuration.Server.Serialization.Settings' because the type requires a JSON object (e.g. {"name":"value"}) to deserialize correctly.
To fix this error either change the JSON to a JSON object (e.g. {"name":"value"}) or change the deserialized type to an array or a type that implements a collection interface (e.g. ICollection, IList) like List<T> that can be deserialized from a JSON array. JsonArrayAttribute can also be added to the type to force it to deserialize from a JSON array.
Path 'settings', line 1, position 88.)
```

or

```
Unhandled exception. Couchbase.Configuration.Server.Serialization.BootstrapException: Could not bootstrap - check inner exceptions for details. (Authentication failed for bucket 'default') (Could not bootstrap with CCCP. (Authentication failed for bucket 'default')) (Cannot deserialize the current JSON array (e.g. [1,2,3]) into type 'Couchbase.Configuration.Server.Serialization.Settings' because the type requires a JSON object (e.g. {"name":"value"}) to deserialize correctly.
 To fix this error either change the JSON to a JSON object (e.g. {"name":"value"}) or change the deserialized type to an array or a type that implements a collection interface (e.g. ICollection, IList) like List<T> that can be deserialized from a JSON array. JsonArrayAttribute can also be added to the type to force it to deserialize from a JSON array.
Path 'settings', line 1, position 88.)
```

Couchbase.Configuration.Server.Serialization.BootstrapException inherits
from System.AggregateException.

In the case of Couuchbase3, we are getting this exception:

```
Unhandled exception. Couchbase.AuthenticationFailureException: Cannot authenticate the user. Reason: AuthenticationError
at Couchbase.Core.IO.Authentication.SaslMechanismBase.SendAsync[T](IOperation`1 op, IConnection connection, CancellationToken cancellationToken)
at Couchbase.Core.IO.Authentication.SaslMechanismBase.SaslStep(IConnection connection, String message, IRequestSpan span, CancellationToken token)
at Couchbase.Core.IO.Authentication.ScramShaMechanism.AuthenticateAsync(IConnection connection, CancellationToken cancellationToken)
at Couchbase.Core.ClusterNode.Couchbase.Core.IO.Connections.IConnectionInitializer.InitializeConnectionAsync(IConnection connection, CancellationToken cancellationToken)
at Couchbase.Core.IO.Connections.ConnectionPoolBase.CreateConnectionAsync(CancellationToken cancellationToken)
```

By returning a 13 return code, we communicate the test framework that
the text can be skipped. This code is processed in
\tracer\test\Datadog.Trace.TestHelpers.AutoInstrumentation\ErrorHelpers.cs

## Reason for change

## Implementation details

## Test coverage

## Other details
<!-- Fixes #{issue} -->

<!-- ⚠️ Note: where possible, please obtain 2 approvals prior to
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Author: NachoEchevarria

tracer/test/test-applications/integrations/Samples.Couchbase/Program.cs

@@ -1,8 +1,10 @@
 using System;
 using System.Collections.Generic;
+using System.Security.Authentication;
 using System.Threading.Tasks;
 using Couchbase;
 using Couchbase.Configuration.Client;
+using Couchbase.Configuration.Server.Serialization;
 using Couchbase.Core;
 using Couchbase.IO;
 
@@ -13,10 +15,29 @@ internal class Program
         ICluster _cluster;
         IBucket _bucket;
 
-        private static async Task Main()
+        private static async Task<int> Main()
         {
             Program p = new Program();
-            await p.RunAllExamples();
+
+            try
+            {
+                await p.RunAllExamples();
+            }
+            catch (AggregateException ex)
+            {
+                Console.WriteLine("Exception during execution " + ex);
+
+                foreach (var exception in ex.InnerExceptions)
+                {
+                    if (exception is AuthenticationException)
+                    {
+                        Console.WriteLine("Exiting with skip code (13)");
+                        return 13;
+                    }
+                }
+            }
+
+            return 0;
         }
 
         private async Task RunAllExamples()

tracer/test/test-applications/integrations/Samples.Couchbase3/Program.cs

@@ -8,14 +8,26 @@ namespace Samples.Couchbase3
 {
     internal class Program
     {
-        private static async Task Main()
+        private static async Task<int> Main()
         {
             var options = new ClusterOptions() 
                       .WithConnectionString("couchbase://" + Host())
                       .WithCredentials(username: "default", password: "password")
                       .WithBuckets("default");
 
-            var cluster = await Cluster.ConnectAsync(options);
+
+            ICluster cluster = null;
+
+            try
+            {
+                cluster = await Cluster.ConnectAsync(options);
+            }
+            catch(AuthenticationFailureException ex)
+            {
+                Console.WriteLine("Exception during execution " + ex);
+                Console.WriteLine("Exiting with skip code (13)");
+                return 13;
+            }
 
             // get a bucket reference
             var bucket = await cluster.BucketAsync("default");
@@ -54,6 +66,8 @@ private static async Task Main()
             {
                 Console.WriteLine("Expected error removing non-existent key: " + ex);
             }
+
+            return 0;
         }
 
         private static string Host()