audit(4): Syscalls to check the accessibility of a file

[aniketp]

Summary

This change introduces the auditability tests for syscalls concerned with checking the
accessibility of files. Categorized under file-attribute-access audit class.

• access(2)
• eaccess(2)
• faccessat(2)

Test Plan

Execute make && make install from test/sys/audit.
Execute kyua test from /usr/tests/sys/audit. All testcases should succeed.

[asomers]

Fixed by r335207 .