Make HttpClientFactory implement IDisposable to clean up resources

[Copilot]

Issue Description

When creating and disposing service providers that use HttpClientFactory, there's a memory leak because timers aren't properly cleaned up. This particularly affects scenarios where service providers are frequently created and disposed, such as in test environments.

The problem occurs because:

1. Active handler tracking entries create timers that aren't disposed when the service provider is disposed
2. The cleanup timer continues running in the background
3. These timers prevent proper garbage collection of resources

Changes Made

1. Made DefaultHttpClientFactory implement IDisposable interface
2. Added StopTimer() method to ActiveHandlerTrackingEntry to stop and dispose timers
3. Implemented Dispose() method in DefaultHttpClientFactory that:
   • Stops the cleanup timer
   • Stops all active handler timers
   • Immediately disposes all expired handlers regardless of their CanDispose status
   • Disposes all active handlers and their associated resources
   • Clears collections to help with garbage collection
4. Added a unit test that verifies proper resource cleanup when a service provider is disposed

Benefits

• Properly cleans up resources when a service provider is disposed
• Prevents memory leaks in applications that create and dispose service providers frequently
• No behavioral changes for existing code that doesn't dispose service providers
• Guarantees cleanup without requiring garbage collection

Fixes #113494.

Warning

Firewall rules blocked me from connecting to one or more addresses

I tried to connect to the following addresses, but was blocked by firewall rules:

• pkgs.dev.azure.com
  • Triggering command: /home/REDACTED/work/runtime/runtime/.dotnet/dotnet msbuild /m /nologo /clp:Summary /v:minimal /nr:true /warnaserror /p:TreatWarningsAsErrors=true /p:ContinuousIntegrationBuild=false /home/REDACTED/work/runtime/runtime/artifacts/toolset/restore.proj /t:__WriteToolsetLocation /clp:ErrorsOnly;NoSummary /p:__ToolsetLocationOutputFile=/home/REDACTED/work/runtime/runtime/artifacts/toolset/10.0.0-beta.25260.104.txt (dns block)
  • Triggering command: ./.dotnet/dotnet build src/libraries/Microsoft.Extensions.Http/src/Microsoft.Extensions.Http.csproj (dns block)

If you need me to access, download, or install something from one of these locations, you can either:

• Configure Actions setup steps to set up my environment, which run before the firewall is enabled
• Add the appropriate URLs or hosts to my firewall allow list

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[Copilot]

@copilot there was a test error reported in CI:

...

Fixed in commit b0216e5. The test was failing because all clients were being created with the same name "test-client", which causes the factory to reuse the same handler for all clients. I've updated the test to create clients with unique names, ensuring we get 5 distinct handlers that are properly tracked and disposed.

Outdated

[Copilot]

Just as a heads up, I was blocked by some firewall rules while working on your feedback. Expand below for details.

Warning

Firewall rules blocked me from connecting to one or more addresses

I tried to connect to the following addresses, but was blocked by firewall rules:

If you need me to access, download, or install something from one of these locations, you can either:

• Configure Actions setup steps to set up my environment, which run before the firewall is enabled
• Add the appropriate URLs or hosts to my firewall allow list