test: Add stress tests

This patch introduces stress tests, which put load on the daemon to help
sanity check its behaviour under stress.

They are separate from the existing integration tests, which focus on
correctness.

Two tests are included here: a load test, which sends emails repeatedly;
and a connection test which opens as many conections as possible.

test/stress-01-load/run.sh

@@ -0,0 +1,31 @@
+#!/bin/bash
+
+set -e
+. $(dirname ${0})/../util/lib.sh
+
+init
+
+generate_certs_for testserver
+add_user user@testserver secretpassword
+
+# Note we run the server with minimal logging, to avoid generating very large
+# log files, which are not very useful anyway.
+mkdir -p .logs
+chasquid -v=-1 --logfile=.logs/chasquid.log --config_dir=config &
+wait_until_ready 1025
+
+echo Peak RAM: `chasquid_ram_peak`
+
+if ! loadgen -logtime -addr=localhost:1025 -run_for=3s -noop; then
+	fail
+fi
+
+echo Peak RAM: `chasquid_ram_peak`
+
+if ! loadgen -logtime -addr=localhost:1025 -run_for=3s; then
+	fail
+fi
+
+echo Peak RAM: `chasquid_ram_peak`
+
+success