[QUIC] Timing fix and more logging

[ManickaP]

Fixes #132000
Contributes to #131950

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[Copilot]

Pull request overview

This PR adjusts System.Net.Quic functional test timing and adds additional diagnostics to help investigate intermittent QUIC test failures (notably around stream-capacity/cancellation and connection-accept behavior).

Changes:

• Updates GetStreamCapacity_OpenCloseStreamCanceledIntoNegative_CountsCorrectly to wait for pending stream-open operations to observe cancellation before asserting capacity increments.
• Tweaks test data structures (lists → arrays) in the same test to better reflect fixed-size usage.
• Adds server-side accept-task logging in CreateConnectedQuicConnection to aid debugging when connection setup fails.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 3 comments.

File	Description
src/libraries/System.Net.Quic/tests/FunctionalTests/QuicTestBase.cs	Converts server accept to a Task and adds logging around accept completion/failure during connection setup exceptions.
src/libraries/System.Net.Quic/tests/FunctionalTests/QuicConnectionTests.cs	Improves cancellation determinism in the stream-capacity test and adjusts how stream/task collections are materialized.

[Copilot]

Pull request overview

Copilot reviewed 2 out of 2 changed files in this pull request and generated no new comments.

Suppressed comments (2)

src/libraries/System.Net.Quic/tests/FunctionalTests/QuicTestBase.cs:256

• This logging prints failed with when serverTask is canceled because Task.Exception is null for canceled tasks. Make the message handle the canceled case explicitly so failures are diagnosable.

                if (serverTask.IsCompleted)
                {
                    _output.WriteLine($"Server {(serverTask.IsCompletedSuccessfully ? "succeeded" : "failed with " + serverTask.Exception)}");
                }

src/libraries/System.Net.Quic/tests/FunctionalTests/QuicConnectionTests.cs:435

• The local variable oce is assigned but never used, which will produce a compiler warning (and in this repo warnings often fail the build). If the exception instance isn't needed, just await the assertion without storing it.

            OperationCanceledException oce = await Assert.ThrowsAsync<OperationCanceledException>(() => Task.WhenAll(pendingClientStreams));