tests: Add ktrace capability violation test cases

Introduce regression tests for ktrace(2) that target capability
violations.

These test cases ensure that ktrace(2) records these violations:

• CAPFAIL_NOTCAPABLE
• CAPFAIL_INCREASE
• CAPFAIL_SYSCALL
• CAPFAIL_SIGNAL
• CAPFAIL_PROTO
• CAPFAIL_SOCKADDR
• CAPFAIL_NAMEI
• CAPFAIL_CPUSET

A portion of these test cases create processes that do NOT enter
capability mode, but raise violations. This is intended behavior.
Users may run ktrace -t p on non-Capsicumized programs to detect
violations that would occur if the process were in capability mode.

Reviewed by: markj
Approved by: markj (mentor)
MFC after: 1 month
Differential Revision: https://reviews.freebsd.org/D40682