[CI Failure] Flaky: AspireServiceBusExtensionsTests.NamespaceWorksInConnectionStrings fails with Collection was modified in AzureEventSourceListener

## Build Information

Build: https://github.com/microsoft/aspire/actions/runs/29602181228
Build error leg or test failing: Tests / Azure.Messaging.ServiceBus / Azure.Messaging.ServiceBus (windows-latest) / `Aspire.Azure.Messaging.ServiceBus.Tests.AspireServiceBusExtensionsTests.NamespaceWorksInConnectionStrings(useKeyed: False)`
Pull request: #15857

## Error Message

```
System.InvalidOperationException : Collection was modified; enumeration operation may not execute.
at System.Collections.Generic.List`1.Enumerator.MoveNext()
at Azure.Core.Diagnostics.AzureEventSourceListener..ctor(Action`1 log, EventLevel level)
at Microsoft.Extensions.Azure.AzureEventSourceLogForwarder.Start()
at Microsoft.Extensions.Azure.AzureClientFactory`2.CreateClient(String name)
```

## Description

Flaky: AspireServiceBusExtensionsTests.NamespaceWorksInConnectionStrings fails with Collection was modified in AzureEventSourceListener

**Type**: flaky-test

## Occurrences

| Date | Build | Job | PR |
|------|-------|-----|----|
| 2026-07-17 | [29602181228](https://github.com/microsoft/aspire/actions/runs/29602181228) | Tests / Azure.Messaging.ServiceBus / Azure.Messaging.ServiceBus (windows-latest) | #15857 |

Start by running AspireServiceBusExtensionsTests.NamespaceWorksInConnectionStrings with useKeyed: False on windows-latest and review the reported AzureEventSourceListener stack trace. Investigate why AzureEventSourceListener encounters a modified collection while Microsoft.Extensions.Azure.AzureEventSourceLogForwarder.Start runs; done means the test no longer flakes with this exception.

Written by the indexing model from the issue text.