Convert using statement to using declaration for ReturnableBufferWriter in GetMemoryUsageInBytes

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Summary

In LinuxUtilizationParserCgroupV2.cs, the GetMemoryUsageInBytes method used a using block statement for ReturnableBufferWriter<char>, which disposed the buffer at the end of the block while memoryFile (a ReadOnlySpan<char> pointing into the buffer) was still used afterward.

This converts it to a using declaration, extending the buffer's lifetime to the method scope and making the code consistent with all other usages of ReturnableBufferWriter in this file and the codebase.

Changes

• Changed using (ReturnableBufferWriter<char> bufferWriter = new(_sharedBufferWriterPool)) to using ReturnableBufferWriter<char> bufferWriter = new(_sharedBufferWriterPool);
• Removed the unnecessary curly braces that scoped the block
• Inlined the memoryFile declaration with its assignment

Microsoft Reviewers: Open in CodeFlow

[Copilot]

Pull request overview

Fixes a buffer lifetime issue in the Linux cgroup v2 memory utilization parser by ensuring a pooled ReturnableBufferWriter<char> remains valid while a ReadOnlySpan<char> that points into it is being consumed.

Changes:

• Replaced a using statement block with a using declaration so the pooled buffer isn’t disposed before memoryFile is processed.
• Removed the extra scope braces and inlined the memoryFile initialization.