profiling: flamegraph export fails with RecursionError on a deeply recursive program

Bug report

Bug description:

The sampling profiler's flamegraph export (profiling.sampling.stack_collector.FlamegraphCollector.export) builds the flamegraph tree with a recursive walk (convert_children) and then serializes it with json.dumps — both recurse to the depth of the deepest sampled stack. The remote unwinder captures up to MAX_FRAMES (1536) frames, but export runs at the default recursion limit (1000), so profiling a program that recurses deeper than ~1000 makes export() raise RecursionError and write no flamegraph. Both --flamegraph and --diff-flamegraph are affected (the diff collector inherits export).

Reachable when profiling a program that raised its own recursion limit and recurses deeply (recursive-descent parsers, tree/graph walkers, deep serializers).

CPython versions tested on:

CPython main

Operating systems tested on:

Linux, macOS

Linked PRs

• gh-156546

profiling/sampling/stack_collector.py の FlamegraphCollector.export と、その convert_children ウォークから始めます。キャプチャされたスタック深度を再帰制限が超える、深く再帰するプログラムを使い、--flamegraph と --diff-flamegraph の両方で再現します。両方のエクスポートパスが RecursionError なしで flamegraph を生成すれば完了です。すでに進行中の作業については、リンクされた PR gh-156546 を確認してください。