[Azure.Messaging.ServiceBus] Fix AmqpMessageBodyTests (Azure#22008)

The `DateTime` and `DateTimeOffset` test values in `AmqpMessageBodyTests.s_amqpValues` were created with `DateTimeOffset.Parse`, which would fail with the following exception when run on a system with a non-US culture:
```
System.TypeInitializationException : The type initializer for 'Azure.Core.Amqp.Tests.AmqpMessageBodyTests' threw an exception.
  ----> System.FormatException : String was not recognized as a valid DateTime.
   at Azure.Core.Amqp.Tests.AmqpMessageBodyTests..ctor()
--FormatException
   at System.DateTimeParse.Parse(String s, DateTimeFormatInfo dtfi, DateTimeStyles styles, TimeSpan& offset)
   at System.DateTimeOffset.Parse(String input)
   at Azure.Core.Amqp.Tests.AmqpMessageBodyTests..cctor()
```

By using `new DateTimeOffset(2021, 3, 24, 0, 0, 0, TimeSpan.Zero)` instead of `DateTimeOffset.Parse("3/24/21")` we ensure that the tests pass on any system regardless of its configured culture.

Author: 0xced

sdk/core/Azure.Core.Amqp/tests/AmqpMessageBodyTests.cs

@@ -27,10 +27,10 @@ public class AmqpMessageBodyTests
             new double[] { 3.1415926 },
             new decimal(3.1415926),
             new decimal[] { new decimal(3.1415926) },
-            DateTimeOffset.Parse("3/24/21").UtcDateTime,
-            new DateTime[] {DateTimeOffset.Parse("3/24/21").UtcDateTime },
-            DateTimeOffset.Parse("3/24/21"),
-            new DateTimeOffset[] {DateTimeOffset.Parse("3/24/21") },
+            new DateTimeOffset(2021, 3, 24, 0, 0, 0, TimeSpan.Zero).UtcDateTime,
+            new DateTime[] { new DateTimeOffset(2021, 3, 24, 0, 0, 0, TimeSpan.Zero).UtcDateTime },
+            new DateTimeOffset(2021, 3, 24, 0, 0, 0, TimeSpan.Zero),
+            new DateTimeOffset[] { new DateTimeOffset(2021, 3, 24, 0, 0, 0, TimeSpan.Zero) },
             TimeSpan.FromSeconds(5),
             new TimeSpan[] {TimeSpan.FromSeconds(5)},
             new Uri("http://localHost"),
@@ -45,8 +45,8 @@ public class AmqpMessageBodyTests
             new Dictionary<string, short> {{ "key", 1 } },
             new Dictionary<string, double> {{ "key", 3.1415926 } },
             new Dictionary<string, decimal> {{ "key", new decimal(3.1415926) } },
-            new Dictionary<string, DateTime> {{ "key", DateTimeOffset.Parse("3/24/21").UtcDateTime } },
-            new Dictionary<string, DateTimeOffset> {{ "key", DateTimeOffset.Parse("3/24/21") } },
+            new Dictionary<string, DateTime> {{ "key", new DateTimeOffset(2021, 3, 24, 0, 0, 0, TimeSpan.Zero).UtcDateTime } },
+            new Dictionary<string, DateTimeOffset> {{ "key", new DateTimeOffset(2021, 3, 24, 0, 0, 0, TimeSpan.Zero) } },
             new Dictionary<string, TimeSpan> {{ "key", TimeSpan.FromSeconds(5) } },
             new Dictionary<string, Uri> {{ "key", new Uri("http://localHost") } },
             new Dictionary<string, Guid> {{ "key", new Guid("55f239a6-5d50-4f6d-8f84-deed326e4554") } },