Stabilize DelegateTests.DelegateAfterReceiverRestart Quarantine test

[karmegams02]

Stabilize DelegateTests.DelegateAfterReceiverRestart

Description

This PR addresses failures in
Microsoft.AspNetCore.Server.HttpSys.FunctionalTests.DelegateTests.DelegateAfterReceiverRestart.

The test could fail after the receiver server was restarted because request delegation continued using a previously created DelegationRule that was no longer valid. This resulted in delegated requests returning HTTP 500 responses instead of reaching the restarted receiver.

To ensure delegation remains functional after a receiver restart, the test now recreates the DelegationRule once the receiver has been restarted and reattached to the request queue.

Validation / Investigation

1. The failure was analyzed and determined to occur after the receiver server restart scenario.
2. The original DelegationRule instance was tied to the previous receiver attachment and became invalid once the receiver was stopped.
3. After the receiver restarted and reattached to the queue, delegation continued using the stale rule rather than creating a new valid delegation target.
4. Recreating the DelegationRule after queue reattachment restores proper request delegation and allows the test to complete successfully.

Changes

1. Recreated the DelegationRule after the receiver restart.
2. Ensured delegation uses the newly attached receiver queue instead of the disposed rule.
3. Preserved the existing test flow while validating successful delegation after receiver recovery.

Fixes #60141.

[dotnet-policy-service]

Thanks for your PR, @karmegams02. Someone from the team will get assigned to your PR shortly and we'll get it reviewed.

[Copilot]

Pull request overview

Stabilizes the DelegateAfterReceiverRestart HttpSys functional test by ensuring request delegation remains valid after the receiver server is restarted and re-attaches to the existing request queue.

Changes:

• Recreates the DelegationRule after the receiver restart so delegation targets the reattached queue.
• Removes the quarantine attribute from DelegateAfterReceiverRestart.