fix: keep semicolons inside xctrace symbols

[tomatotomata]

Summary

xctrace folded stacks use semicolons to separate frames. Rust demangling can introduce semicolons inside array types such as [u8; 2], so those symbols were being split into multiple frames.

I was thinking of applying the same normalization already used by inferno's DTrace collapser: replace semicolons inside the demangled symbol with colons before the XML reaches the xctrace collapser. The change is limited to the macOS demangling path and includes a regression test for an array type.

Validation

• cargo fmt -- --check
• cargo test --all-targets
• git diff --check

The test suite passed on Windows. I could not run the macOS-only test locally because the Apple target is not installed here.

This follows the maintainer's invitation in #462. Let me know what you think.

[djc]

Thanks!