stackwalk: initialize glibc pointer demangling eagerly
Lazy initialization can run the setjmp probes on a signal-handler stack during the first simulated longjmp. The probes are signal-safe, but normal startup offers a simpler environment and avoids making signal delivery responsible for initialization.
Initialize the scheme while installing Linux signal handlers and retain the lock-free lazy path for alternate startup configurations and defensive fallback.
Co-authored-by: OpenAI Codex <noreply@openai.com>
