And explain that we're waiting for bridges

Analysis tools such as vulture treat functions configure, restart, and
wait_for_bootstrap in Network as unused, when in reality they are called
from the ./chutney commandline. Make this explicitly clear.

Running flake8 on lib/chutney/*.py caught a few typographical errors and
oversights.

Leave Node.specialize() uncommented because I don't know what this does
yet (it looks unused) but document other interfaces where necessary and
clean up comments.

From subprocess.check_output() in run_tor().

In NodeController and NodeBuilder abstract base classes, make it clearer
which methods to override and give runtime errors if these are called
and not overriden.

In Templating.py and TorNet.py

Avoids race conditions where chutney tells tor to exit twice.
And where chutney tells unrelated processes to exit.

Part of 33793.

After stopping, it can take a little while for tor to cleanup.
Wait a few extra seconds, to avoid race conditions.

Part of 33793.

Microdescriptor search in #33428 is almost finished, so change the
comment to refer to onion service descriptor search in #33609.

If there is a time calculation bug, or a large clock skew, fail
bootstrap.

Diagnostics for macOS Travis hangs.

chutney was calculating some elapsed times incorrectly, leading to longer
wait times for network bootstrap.

Bugfix on 33615.

chutney was displaying any node set without directory authorities as
"caches and clients".

Now, chutney only displays "caches and clients" if the node set contains
all caches and clients, and no dir auths.

Bugfix on 33615.

Bugfix on 33615.

Some legacy Tor versions (0.3.5 and earlier) have microdescriptor
download bugs. Chutney triggers those bugs by verfying early, and
rapidly reconnecting to the SOCKSPort (#33598).

So chutney waits for a minimum amount of time after launching the
network (65 seconds on 0.3.5 and earlier), regardless of bootstrap
status or directory info distribution.

We also change the unchecked descriptor wait time to:
  * 10 seconds for microdesc downloads, and
  * 30 seconds for onion services to publish their descriptors.

Fixes bug 33615.

Preparation for 33615.

Documentation for 33379.

Cleanup after 33361.

Previously, the script reset the number of failures to 1.

Fix on 33583.

Set CHUTNEY_ALLOW_FAILURES to 2, so that CI tolerates a single failure
during each test-network.sh run.

Part of 33583.

We want to make sure tor has fully exited, and the OS has reclaimed
its resources.

The pause helps if the failure happened due to system load.

Part of 33583.

The current script output makes it easy to confuse bootstrap attempts
and verify rounds.

Change the output to make it clearer.

Part of 33583.