Fix cdbstack parser dropping last sample and missing metrics

[Copilot]

Fix for cdbstack - last sample is dropped (Issue)

Plan

• Explore repository and understand the issue
• Understand the bug: last sample in file not added when EOF is reached
• Create test case to demonstrate the bug
• Fix the bug by adding code after the for loop to handle the last sample
• Ensure sample.Metric = 1 is set (related to issue No metrics in cdbstacks #1009)
• Build and test the changes (TraceEvent builds successfully)
• Manual code review completed
• Logic verification completed
• Refactor to extract helper method (addressing code review feedback)
• Finalize and complete

Changes Made

1. Extracted helper method: Created AddSampleFromStack() method to eliminate code duplication
2. Line 113 & 124: Both call sites now use the helper method
3. Test file: Comprehensive test cases in DebuggerStackSourceTests.cs

Refactoring Details

• Created AddSampleFromStack() helper method that encapsulates the logic for:
  • Building the call stack from accumulated frames
  • Setting sample.Metric = 1
  • Setting sample properties (StackIndex, TimeRelativeMSec)
  • Adding the sample
• Both locations (line 94 and line 118 in original) now call this helper
• Eliminates ~15 lines of duplicated code

Issue Resolution

This PR fully resolves the reported issue where the last sample in a cdbstack file was being dropped at EOF, and addresses the code review feedback to eliminate duplication.

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[brianrob]

@copilot, please address this comment.

[brianrob]

Copilot Post-Mortem:

• Bonus points for detecting that there was another issue in the same area (it was referenced) and fixing them both together.

[leculver]

LGTM