[Internal] CI: Adds meaningful failure message on assert failure (#5513)

## Description

The test randomly fails with `Assert.IsTrue()` failed, without enough
context on what is failing. Adding information useful for the context

## Type of change

- [x] Bug fix (non-breaking change which fixes an issue)

Author: yash2710

Microsoft.Azure.Cosmos/tests/Microsoft.Azure.Cosmos.EmulatorTests/CosmosAvailabilityStrategyTests.cs

@@ -267,12 +267,14 @@ public async Task AvailabilityStrategyNoTriggerTest(bool isPreferredLocationsEmp
                 if (isPreferredLocationsEmpty)
                 {
                     Assert.IsTrue(traceDiagnostic.ToString()
-                        .Contains($"\"Hedge Context\":[\"{region1}\",\"{region2}\",\"{region3}\"]"));
+                        .Contains($"\"Hedge Context\":[\"{region1}\",\"{region2}\",\"{region3}\"]"),
+                            $"{traceDiagnostic} does not contain expected regions \"{region1}\", \"{region2}\", \"{region3}\"");
                 }
                 else
                 {
                     Assert.IsTrue(traceDiagnostic.ToString()
-                        .Contains($"\"Hedge Context\":[\"{region1}\",\"{region2}\"]"));
+                        .Contains($"\"Hedge Context\":[\"{region1}\",\"{region2}\"]"), 
+                            $"{traceDiagnostic} does not contain expected regions \"{region1}\", \"{region2}\"");
                 }
             }
             ;