feat(ctrace): recognize PMU trace-on-overflow packets

[thorstendb-ARM]

Summary

Prepare ctrace to safely handle PMU trace-on-overflow packets without adding PMU output semantics yet.

• Recognize DWT discriminator 3 as a PMU trace-on-overflow packet.
• Preserve the OVn counter mask in a dedicated PmuTraceEvent.
• Preserve packet index, stream ID, timestamp, and trace quality through post-decoding.
• Keep PMU events excluded from CSV and CTF output until their configuration and output semantics are implemented.
• Verify that subsequent trace packets continue to be processed normally.

Scope

This PR only adds decoding groundwork. It intentionally does not expose PMU events through CSV, CTF, or trace selection.

Tests

• Unit coverage for DWT and Cortex-M post-decoding.
• Raw OpenCSD pipeline coverage.
• End-to-end test confirming that PMU packets are ignored without errors while following ITM packets and output generation remain intact.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 72.40%. Comparing base (01d1c3f) to head (d2505ef).

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #2589   +/-   ##
=======================================
  Coverage   72.40%   72.40%           
=======================================
  Files         185      185           
  Lines       30393    30401    +8     
  Branches    17927    17929    +2     
=======================================
+ Hits        22005    22013    +8     
  Misses       6079     6079           
  Partials     2309     2309           

Flag	Coverage Δ
ctrace-cov	99.81% <100.00%> (+<0.01%)	⬆️

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Files with missing lines	Coverage Δ
tools/ctrace/src/decode/DwtPacketDecoder.cpp	100.00% <100.00%> (ø)
tools/ctrace/src/model/TraceEvent.h	100.00% <ø> (ø)

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[github-actions]

Test Results

  4 files    4 suites   1s ⏱️
191 tests 191 ✅ 0 💤 0 ❌
382 runs  375 ✅ 7 💤 0 ❌

Results for commit d2505ef.