[release/5.0] Fix polling on https connections in HttpConnectionPool

[scalablecory]

Backport of #49474 to release/5.0

Customer Impact

With this fix, customers with large numbers of HTTPS connections will see significantly less pinning, and avoid GC behavior caused by long-lived pins.

A customer is blocked on deploying 5.0 due to this.

Testing

Verified in private build by customer.

Risks

Most users of HttpClient will be affected by this code change, so I wouldn't say there is zero risk. However, this returns HTTPS behavior to what worked prior to 5.0, so the ramifications are well understood.

[ghost]

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Issue Details

---

Backport of #49474 to release/5.0

Customer Impact

With this fix, customers with large numbers of HTTPS connections will see significantly less pinning, and avoid GC behavior caused by long-lived pins.

A customer is blocked on deploying 5.0 due to this.

Testing

Verified in private build by customer.

Author:	scalablecory
Assignees:	scalablecory
Labels:	Servicing-consider, area-System.Net.Http, tenet-performance
Milestone:	5.0.x

[danmoseley]

@scalablecory (or @stephentoub ) can you please add a risk statement above? Also please share with me (internally) a bit more about the customer.

[scalablecory]

@scalablecory (or @stephentoub ) can you please add a risk statement above? Also please share with me (internally) a bit more about the customer.

Added, and I pinged you with some more info.

[danmoseley]

Unrelated failures:

    System.Diagnostics.Tests.ProcessTests.TestExited_SynchronizingObject(invokeRequired: True) [FAIL]
      Assert.NotNull() Failure
      Stack Trace:
        /_/src/libraries/System.Diagnostics.Process/tests/ProcessTests.cs(162,0): at System.Diagnostics.Tests.ProcessTests.TestExited_SynchronizingObject(Boolean invokeRequired)

[danmoseley]

@dotnet/dnceng this build seems to have been unscheduled for a long time.
https://dev.azure.com/dnceng/public/_build/results?buildId=1073977&view=logs&j=8c86bf4a-7db8-5975-0225-f9a7d8a16765
Work has been submitted to the Helix API (BuildPool.Windows.10.Amd64.VS2019.Open), but has not started yet (Helix work item in job ab8f479f-654d-462f-a293-48d54e0c3425 for agent 1cb2bfed-8fd4-473c-926d-e7c3c07ec051 is currently Unscheduled, machines are either busy or provisioning)

Could you please check?

[jonfortescue]

@danmoseley Taking a look.

[jonfortescue]

@danmoseley this is related to an ongoing Azure IcM described in https://github.com/dotnet/core-eng/issues/12732. There's an email out to partners with more details on what's going on.

[danmoseley]

@Anipik i believe this is good to merge