Delayed init was introduced 2019-02-19 in ef5e30056 and was lazy init at
that time, matching the name.
This changed 2020-05-19 in 4eb78f5c8, when auto-init was added, making
delayed init not delayed anymore.
While the option is still needed to make manual lifetime work, and it has
to be enabled on apple, there's no reason anymore to expose it to users.
- Loop startup waitpid on EINTR; kill and reap the child on fatal error
or when interrupted, instead of leaking a ptrace-stopped process.
- Treat PTRACE_DETACH failure as fatal -- otherwise the child is stuck
stopped forever.
- Zero-initialize procName so the memcpy into ___tracy_magic_process_name
does not copy uninitialized stack past the NUL.
- Forward SIGINT to the child from the signal handler when in forked
mode, so Ctrl-C during a blocking waitpid unblocks cleanly.
- Preflight perf_event_open on the target before StartupProfiler so
permission failures surface with actionable guidance instead of
silently producing no samples.
- Also handle SIGHUP and SIGQUIT.
