lib: Automated cleanup of cdefs and other formatting

Apply the following automated changes to try to eliminate
no-longer-needed sys/cdefs.h includes as well as now-empty
blank lines in a row.

Remove /^#if.*\n#endif.*\n#include\s+<sys/cdefs.h>.*\n/
Remove /\n+#include\s+<sys/cdefs.h>.*\n+#if.*\n#endif.*\n+/
Remove /\n+#if.*\n#endif.*\n+/
Remove /^#if.*\n#endif.*\n/
Remove /\n+#include\s+<sys/cdefs.h>\n#include\s+<sys/types.h>/
Remove /\n+#include\s+<sys/cdefs.h>\n#include\s+<sys/param.h>/
Remove /\n+#include\s+<sys/cdefs.h>\n#include\s+<sys/capsicum.h>/

Sponsored by: Netflix

Remove $FreeBSD$: one-line .c pattern

Remove /^[\s*]*__FBSDID\("\$FreeBSD\$"\);?\s*\n/

spdx: The BSD-2-Clause-FreeBSD identifier is obsolete, drop -FreeBSD

The SPDX folks have obsoleted the BSD-2-Clause-FreeBSD identifier. Catch
up to that fact and revert to their recommended match of BSD-2-Clause.

Discussed with: pfg
MFC After: 3 days
Sponsored by: Netflix

cap_dns tests: Convert to ATF, avoid failing when lookups don't resolve

The cap_dns tests require Internet access. Currently they fail when
that's not available, which for CI purposes is undesirable. Let's
instead skip the tests if none of the non-casper name/addr lookups
succeed.

To that end:
- Convert the tests to ATF so that skipping is easier to implement.
- Break up the tests into separate test cases.
- If one of the system (i.e., non-casper) lookup functions fails, skip
the test if all of them failed, otherwise fail the tests, since
partial failure indicates something is flaky and deserves a closer
look.

Reviewed by: oshogbo
MFC after: 1 week
Differential Revision: https://reviews.freebsd.org/D39241

libcasper: ange the name of limits in cap_dns so the intentions are obvious.

Reported by: pjd
MFC after: 3 weeks

libcasper: fix limitations in dns service

The getaddrinfo(3) and gethostbyname(3) are used to return the address for a
given hostname. The getnameinfo(3) and gethostbyaddr(3) are used to return
hostname for a given address. Right now in casper, we have two limitations:
- NAME which allows resolving DNS names.
- ADDR which allows to do revert DNS lookups.

Before this change the rights was mixed up:
NAME - getnameinfo(3) and gethostbyname(3)
ADDR - gethostbyaddr(3) and getaddrinfo(3)

Which no matters on limitation allowed us to resolve DNS names and do DNS
lookups basically by using a different set of functions.

Now the NAME type allows getaddrinfo(3) and gethostbyname (3)functions,
and the ADDR names allow to use gethostbyaddr(3) and getnameinfo(3) functions.

Reviewed by: pjd, bcr
MFC after: 3 weeks
Discussed with: hrs
Differential Revision: https://reviews.freebsd.org/D16930

Add SPDX tags for libcasper(3) and services.

MFC after: 2 weeks

Introduce caspermocks.

The idea behinds mocks is that we don't need to ifdef a lot of code in
tools itself but those defines are hidden in the casper library.
Right now the mocks are implemented as define/inlines functions.
There was a very long discussion how this should be implemented.
This approach has some advantages like we don't need to link to any additional
libraries. Unfortunately there are also some disadvantages for example it is
easy to get library out of sync between two versions of functions or that we
need extra define to compile program with casper support.
This isn't an ideal solution but it's good enough for now and should simplify
capsicumizing programs. This also doesn't close us any other ways to do those
mocks and this should evolve in time.

Discussed with: pjd, emaste, ed, rwatson, bapt, cem, bdrewery
Differential Revision: https://reviews.freebsd.org/D8753

Use hardcoded IPv4/IPv6 addresses for google-public-dns-a.google.com instead
of freefall.freebsd.org to unbreak the DNS tests

The address allocations for freefall.freebsd.org have changed in the past 4 years.
Use a more stable set of hardcoded addresses for now to make the tests succeed
reliably.

The hostname should be resolved dynamically instead of hardcoding the addresses in
the future. This is just a bandaid.

MFC after: 1 week

Fix result printing

- Flushing stdout prevents the buffer from being printed twice, fixing
issues with stdout printing out the testplan, etc, twice.
- Don't print out raw source/line numbers; hide them behind comments.

MFC after: 1 week

Move libcasper tests from regression/capsicum/libcasper/ to
lib/libcasper/service/${service_name}/tests.

Reviewed by: emaste, ngie
Differential Revision: https://reviews.freebsd.org/D7759