Fix test duration display to not show "(0ms)" when duration is unavailable

[Copilot]

When test duration is null, it was being converted to TimeSpan.FromTicks(0) and displayed as "(0ms)", which is misleading since the duration is actually unknown, not zero.

Changes

• TestApplicationHandler.cs: Pass null when testResult.Duration is not available instead of TimeSpan.FromTicks(0)
• TerminalTestReporter.cs: Accept TimeSpan? in TestCompleted and RenderTestCompleted, only render duration when value is present

// Before
TimeSpan.FromTicks(testResult.Duration ?? 0)  // Shows "(0ms)" when null

// After  
testResult.Duration.HasValue ? TimeSpan.FromTicks(testResult.Duration.Value) : null  // Omits duration when null

Output changes from passed TestName (0ms) to passed TestName when duration is unavailable.

Original prompt

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This section details on the original issue you should resolve

<issue_title>Test duration shouldn't be shown as 0 if no value was provided</issue_title>
<issue_description>Example:

sdk/src/Cli/dotnet/Commands/Test/MTP/TestApplicationHandler.cs

Line 146 in 7538a89

TimeSpan.FromTicks(testResult.Duration ?? 0),

If duration was null, we show it as "0". That doesn't look correct. We shouldn't print the duration at all in this case, because it's simply unknown.</issue_description>

Comments on the Issue (you are @copilot in this section)

• Fixes Test duration shouldn't be shown as 0 if no value was provided #51544

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[nohwnd]

Feels to me more like an "error" state where it should say (unknown ms) or (? ms). Is there a legitimate reason for framework to not report the amount of time it took? And if the data are missing will the user notice without us telling them something is missing?

[Youssef1313]

It's a test framework decision. In 99% of the cases, I think the data will be there.
I only hit it in our internal test framework for MSTest, and showing 0ms was misleading.

[nohwnd]

Ok