test/e2e: add random testnet generator (#5479)

Closes #5291. Adds a randomized testnet generator. Nightly CI job will be submitted separately. A few of the testnets can be a bit flaky, even after disabling known-faulty behavior and making minor tweaks, and the larger networks may be too resource-intensive to run in CI - this will be optimized separately.

test/e2e/run-multiple.sh

@@ -0,0 +1,35 @@
+#!/usr/bin/env bash
+#
+# This is a convenience script that takes a list of testnet manifests
+# as arguments and runs each one of them sequentially. If a testnet
+# fails, the container logs are dumped to stdout along with the testnet
+# manifest.
+#
+# This is mostly used to run generated networks in nightly CI jobs.
+#
+
+# Don't set -e, since we explicitly check status codes ourselves.
+set -u
+
+if [[ $# == 0 ]]; then
+	echo "Usage: $0 [MANIFEST...]" >&2
+	exit 1
+fi
+
+for MANIFEST in "$@"; do
+	START=$SECONDS
+	echo "==> Running testnet $MANIFEST..."
+	./build/runner -f "$MANIFEST"
+
+	if [[ $? -ne 0 ]]; then
+		echo "==> Testnet $MANIFEST failed, dumping manifest..."
+		cat "$MANIFEST"
+
+		echo "==> Dumping container logs for $MANIFEST..."
+		./build/runner -f "$MANIFEST" logs
+		exit 1
+	fi
+
+	echo "==> Completed testnet $MANIFEST in $(( SECONDS - START ))s"
+	echo ""
+done