ktrace: Record signal violations with KTR_CAPFAIL

Report the delivery of signals to processes other than self while
Capsicum violation tracing with CAPFAIL_SIGNAL.

Reviewed by: markj
Approved by: markj (mentor)
MFC after: 1 month
Differential Revision: https://reviews.freebsd.org/D40679

(cherry picked from commit 6a4616a529c1e387d87376e48ceb670eef8141e7)