kern: add bounds-safety soft-trap runtime

[abhijeetsharma2002_gmail.com]

Summary

__bounds_safety_soft_trap() counts violations via counter(9), fires a
SDT probe carrying the trap site, and continues instead of panicking.
Console logging is opt-in and rate-limited. The deliberate-violation
test hook lives in a separate file so enabling it never instruments the
handler itself.

Sponsored by: The FreeBSD Foundation

[rpaulo]

sys/kern/kern_bounds.c

82

You can remove some empty lines in this function.

92

We do need to get a backtrace, otherwise it’s not very useful IMO.
Can you check how WITNESS does this?

[abhijeetsharma2002_gmail.com]

Address code review