This reverts commit 75449088.

I need the test suite working to release 3.0~beta2, and it's been quite broken
on feature/stretch since the merge of test/12059-dogtail-optimizations.

refs: #12305

We have decided to remove I2P (Refs: #11276) due to our failure of
finding someone interested in maintaining it in Tails.

Will-fix: #12263

It will run an arbitrary shell command when pause() is called, e.g. on
failure when --interactive-debugging is used. This is pretty useful
when multitasking with long test suite runs, so you immediately are
notified when a test fails (or when you reached a temporary pause()
breakpoint).

Will-fix: #12175

I dropped it by mistake when modifying pause() for
--interactive-debugging.

It does the same thing, but also offers an interactive Ruby shell via
pry in the Cucumber world context.

For now, let's just focus on remote shell timeouts, and for that let's
be really sure we only catch *remote shell* timeouts, and not try_for()
timeouts thrown from "outside" when wrapping around remote shell usage.

... after 20 minutes, by default, and it is no coincidence that it is
distinctly lower than our Jenkins' setup's timeout. For commands that
may require longer timeout (or none) there's an option.

Most terminal emulators will send a notification of some sort when and
ASCII bell is received, which is pretty helpful for --pause-on-fail, and
if you add temporary pause():es while debugging.

Just like in try_for().

See the large comment added in this commit for details.

This reverts commit 5dae9681.

I missed that force_new_tor_circuit() was used elsewhere when I
removed it in the reverted commit.

The old design was very inflexible, which over time lead to the
implementation growing messy as different checks were added. The
issue was that it had to hard-code the particular checks we
wanted, and did not allow the user to formulate an expression for
which packets are considered leaks or not. So, let's instead
provide an assertion-like function to which the user passes a
block describing how we want all our packets to look.

Furthermore, now all firewall leak tests should be ok with the
simulated Tor network provided by Chutney. Since all Tor nodes
(incl. bridges) run from the same host (and IP address) we also
include the server port when verifying that no unexpected hosts were
contacted.

Note that in some cases we've lost a bit of information and
precision, e.g. among the anti-tests we no longer exactly match
the protocol that was leaked, but that wasn't very valuable to
begin with, and instead we test *exactly* the code that these are
anti tests for -- a true anti test, indeed!

Also, the 'no traffic has flowed to the LAN' (now renamed) had a
serious bug which was fixed in passing -- the `@lan_host`
variable was not set, so it is `nil`, which could never be among
the IPv4 TCP leaks, so that step always succeeded! :S

... provided by Chutney (https://gitweb.torproject.org/chutney.git).
This is enabled iff the local configuration contains something like:

  Chutney:
    src_dir: "/path/to/chutney-src-tree"

otherwise we'll use the real Tor network as we done previously.

The main motivation here is improved robustness -- since the "Tor
network" we now use will exit from the host running the automated test
suite, we won't have to deal with Tor network blocking. Performance
should also be improved.

Will-fix: #9521

A well-placed `pause()` can act as a breakpoint when debugging.

Test suite: use the Journal instead of the deprecated /var/log/syslog to extract debugging information about restart-tor.

We do this elsewhere (outside of the automated test suite), so let's
be consistent.

Will-fix: #10151

This makes it easier to see what belongs to which run. While we're at
it we also improve the names so they actually refer to the scenario
that failed.

Will-fix: #10151

This will help troubleshoot those instances in which Tor may not
bootstrap within the time we wait (currently 270 seconds).

Some details can be gleamed from:

    * http://www.jonathanleighton.com/articles/2012/stop-test-unit-autorun/
    * https://stackoverflow.com/questions/15572257/how-to-stop-rspec-from-running-test-unit-at-the-end

There's some code simplification too, and the removal of the
@new_circuit_tries counter, which is all over the place and is a bit
hard to keep track of.

Also for the wget/whois test we do not try to detect if Tor was the
problem and only force a new circuit (and hence count it as a retry),
since that could lead to an infinite loop. With the new helper, we
always do MAX_NEW_TOR_CIRCUIT_RETRIES number of retries.

I fear we'll get some very hard to debug errors if this limitation is
forgotten some time in the future, so let's be proactive. Also, switch
back to throwing Timeout::Error on failure, since it basically is a
wrapper around it.

That means all but those where we rely on the shell, e.g. when we
dot-include a file and chain a command with ; or && like this:

    . path/to/config; echo $var_in_config