fix(allocations): stop the heap sampling when getting profile

[IlyasShabi]

What does this PR do?:

In ts/src/heap-profiler.ts, after each profile() call in allocation mode, stop and immediately restart the V8 sampling heap profiler with the original parameters. The stop call frees V8's sample buffer; the restart resumes sampling for the next window.

Motivation:

When the heap profiler is started with allocations enabled, V8 retains a record of every sampled allocation. The only V8 API that frees that buffer is StopSamplingHeapProfiler and GetAllocationProfile does not clear it.

Today the binding never restarts the sampler between collections. Each call to profile() re-aggregates the entire history of sampled allocations since the profiler was started, producing two issues:

1. Reported alloc_* totals grow ~N× across N consecutive profile() calls instead of reflecting the per-window allocation rate.
2. V8's internal sample buffer grows for the lifetime of the process (memory leak)

Additional Notes:
Benchmark

Baseline

  #  pprof_samples   alloc_MiB   inuse_MiB     alloc_objects   ratio_vs_#1
   1              8    5589.60       1.93        366117116     1.00x
   2             10   11202.27       2.43        733927295     2.00x
   3             11   16864.94       2.43       1104955079     3.02x
   4             11   22508.62       2.43       1474818782     4.03x
   5             13   28424.36       2.49       1862485415     5.09x

With the Fix

  #  pprof_samples   alloc_MiB   inuse_MiB     alloc_objects   ratio_vs_#1
   1              6    5656.60       1.93        370557315     1.00x
   2              6    5635.10       2.43        369125338     1.00x
   3              4    5625.60       2.43        368536560     0.99x
   4              5    5589.10       1.93        366109674     0.99x
   5              7    5893.67       1.99        386073436     1.04x

[github-actions]

Overall package size

Self size: 2.19 MB
Deduped: 2.89 MB
No deduping: 2.89 MB

Dependency sizes

| name | version | self size | total size | |------|---------|-----------|------------| | pprof-format | 2.2.2 | 500.53 kB | 500.53 kB | | source-map | 0.7.6 | 185.63 kB | 185.63 kB | | node-gyp-build | 4.8.4 | 13.86 kB | 13.86 kB |

_{🤖 This report was automatically generated by heaviest-objects-in-the-universe}

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