src: expose size and count in heap profile output

[IlyasShabi]

v8.startHeapProfile().stop() returns the sampling heap profile in the CDT format. That format reports only size (= objectSize × objectCount) per sample and selfSize per node, discarding the object count and the live/collected distinction that V8 already tracks.

In this PR every existing CDT field keeps its name and value, and :

• Nodes: add selfCount (number of sampled objects) alongside selfSize (total bytes).
• Samples: add objectSize, objectCount, and isLive.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 89.98%. Comparing base (5ed55ba) to head (55080ea).
⚠️ Report is 5 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #65737      +/-   ##
==========================================
- Coverage   90.05%   89.98%   -0.07%     
==========================================
  Files         754      755       +1     
  Lines      256518   257288     +770     
  Branches    48534    48772     +238     
==========================================
+ Hits       231007   231527     +520     
- Misses      16609    16863     +254     
+ Partials     8902     8898       -4     

Files with missing lines	Coverage Δ
src/node_profiling.cc	82.50% <100.00%> (+1.41%)	⬆️

... and 45 files with indirect coverage changes

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