[BUG] Is ClientDiagnostics's DiagnosticListener leaking?

[tg-msft]

An internal partner is seeing a leak caused by:

• ClientDiagnostics derives from DiagnosticScopeFactory
• DiagnosticScopeFactory creates a DiagnosticListener
• DiagnosticListener disposal removes itself from a global list
• We don't dispose ClientDiagnostics.

Should we add a destructor on DiagnosticScopeFactory that disposes its listener?

[pakrym]

Related: microsoft/ApplicationInsights-dotnet#1867

[pakrym]

We can go about it in two ways:

1. Add a finalizer to the DiagnosticScopeFactory
2. Cache DiagnosticListener in a dictionary based on the namespace.

The latter would cause fewer allocations per-client instance and I suspect we'll need a similar thing for ActivitySource support pretty soon as well.

[kasobol-msft]

Azure Storage SDK included this fix in the release today. Package versions can be found here