profiling: --collapsed export fails with UnicodeEncodeError on non-ASCII frame names

Bug report

Bug description:

CollapsedStackCollector.export (Lib/profiling/sampling/stack_collector.py) opens its output with open(filename, "w") — no encoding=. It is the only exporter in that module missing it; FlamegraphCollector.export, the JSONL exporter and the heatmap exporter all pass encoding="utf-8". Because the collapsed format writes frame names verbatim (the JSON exporters escape non-ASCII via ensure_ascii), --collapsed export raises UnicodeEncodeError when a sampled frame's function or file name contains non-ASCII characters under a non-UTF-8 locale, or surrogate-escaped characters (from an undecodable path) on any locale:

UnicodeEncodeError: 'ascii' codec can't encode characters ...
UnicodeEncodeError: 'utf-8' codec can't encode character '\udc80' ... surrogates not allowed

Non-English identifiers are common and non-UTF-8 locales are supported, so profiling such a program with --collapsed produces no output and an uncaught error.

CPython versions tested on:

CPython main

Operating systems tested on:

Linux, macOS

Linked PRs

• gh-156811
• gh-156814

Iniziate da Lib/profiling/sampling/stack_collector.py e confrontate CollapsedStackCollector.export con gli altri exporter che specificano un output UTF-8. Controllate prima le PR collegati gh-156811 e gh-156814; è completato quando l'export collapsed riesce per i nomi dei frame non ASCII e sottoposti a escape con surrogate, senza UnicodeEncodeError.