Benchmark: Add real-life configuration file and benchmark wrapper

Performance on this real-life configuration:

Before last commit:
Service runtime: 2min 22.669s
CPU time consumed: 3min 44.299s
Memory peak: 50.7M (swap: 0B)

With last commit:
Service runtime: 7.569s
CPU time consumed: 21.998s
Memory peak: 105.6M (swap: 0B)

bench/bench.sh

@@ -0,0 +1,24 @@
+set -e
+
+if test "$(realpath "$PWD")" != "$(realpath "$(dirname "$0")/..")"
+then
+	echo "You must be in reaction root directory"
+	exit 1
+fi
+
+if test ! -f "$1"
+then
+	# shellcheck disable=SC2016
+	echo '$1 must be a configuration file (most probably in ./bench)'
+	exit 1
+fi
+
+rm -f reaction.db 
+cargo build --release 
+sudo systemd-run --wait \
+	-p User="$(id -nu)" \
+	-p MemoryAccounting=yes \
+	-p IOAccounting=yes \
+	-p WorkingDirectory="$(pwd)" \
+	-p Environment=PATH=/run/current-system/sw/bin/ \
+	sh -c "for i in 1 2; do ./target/release/reaction start -c '$1' -l ERROR -s ./reaction.sock; done"