dtrace tests: Require perl

A number of tests use it, so just require it globally as we do with
other tools.

MFC after: 1 week

dtrace: Add the 'oformat' libdtrace option

This option can be used to specify a format to use in DTrace output.
The following formats are supported:
- json
- xml
- html
- none (default DTrace output)

This is implemented using libxo and integrated into libdtrace. Client
code only works with the following API:

- dtrace_oformat_setup(dtrace_hdl_t *) -- to be called when output is starting.
- dtrace_oformat_teardown(dtrace_hdl_t *) -- to be called when output is finished
- dtrace_oformat(dtrace_hdl_t *) -- check if oformat is enabled.
- dtrace_set_outfp(FILE *) -- sets the output file for oformat.
- Ensure that oformat is correctly checked in the drop handler and record
processing callbacks.

This commit also adds tests which check if the generated output is
valid (JSON, XML) and extends the dtrace(1) describing the structured output.

Reviewed by: markj
Discussed with: phil
MFC after: 2 months
Sponsored by: Innovate UK
Differential Revision: https://reviews.freebsd.org/D41745

Remove $FreeBSD$: one-line sh pattern

Remove /^\s*#[#!]?\s*\$FreeBSD\$.*$\n/

dtrace tests: Support globbing for excludes

Downstream this makes skipping tests like common/ip/tst.*sctp*.ksh simpler.

Reviewed by: vangyzen, cem, markj
Sponsored by: Dell EMC
Differential Revision: https://reviews.freebsd.org/D24608

Fix DTrace test ATF wrapper generation.

Merge ^/user/ngie/release-pkg-fix-tests to unbreak how test files are installed
after r298107

Summary of changes:

- Replace all instances of FILES/TESTS with ${PACKAGE}FILES. This ensures that
namespacing is kept with FILES appropriately, and that this shouldn't need
to be repeated if the namespace changes -- only the definition of PACKAGE
needs to be changed
- Allow PACKAGE to be overridden by callers instead of forcing it to always be
`tests`. In the event we get to the point where things can be split up
enough in the base system, it would make more sense to group the tests
with the blocks they're a part of, e.g. byacc with byacc-tests, etc
- Remove PACKAGE definitions where possible, i.e. where FILES wasn't used
previously.
- Remove unnecessary TESTSPACKAGE definitions; this has been elided into
bsd.tests.mk
- Remove unnecessary BINDIRs used previously with ${PACKAGE}FILES;
${PACKAGE}FILESDIR is now automatically defined in bsd.test.mk.
- Fix installation of files under data/ subdirectories in lib/libc/tests/hash
and lib/libc/tests/net/getaddrinfo
- Remove unnecessary .include <bsd.own.mk>s (some opportunistic cleanup)

Document the proposed changes in share/examples/tests/tests/... via examples
so it's clear that ${PACKAGES}FILES is the suggested way forward in terms of
replacing FILES. share/mk/bsd.README didn't seem like the appropriate method
of communicating that info.

MFC after: never probably
X-MFC with: r298107
PR: 209114
Relnotes: yes
Tested with: buildworld, installworld, checkworld; buildworld, packageworld
Sponsored by: EMC / Isilon Storage Division

Rename Makefile.inc1 to dtrace.test.mk to avoid clash with top-level Makefile.inc1.

Discussed with: ngie, markj
Sponsored by: EMC / Isilon Storage Division