Add 'load directly' mode to default Cucumber test suite (#6664)

Currently `npm test` runs the Cucumber suite with a matrix
configuration for selecting the algorithm (CH, MLD) and data loading
(shared-memory, mmap) options.

However, there is a third data loading option, 'load directly',
which is to directly load the datasets into the osrm-routed process memory.

The code paths for each data loading option are distinct:

Storage::Run + SharedMemoryAllocator
MMapMemoryAllocator
ProcessMemoryAllocator

This commit adds direct data loading as part of the Cucumber
configuration matrix.

This will ensure optional dataset support can be added without any
regressions.

scripts/cucumber_test_matrix.sh

@@ -0,0 +1,18 @@
+#!/usr/bin/env bash
+
+set -o errexit
+set -o pipefail
+set -o nounset
+
+loadmethods=(datastore mmap directly)
+profiles=(ch mld)
+
+for profile in "${profiles[@]}"
+do
+  for loadmethod in "${loadmethods[@]}"
+  do
+    set -x
+    node ./node_modules/cucumber/bin/cucumber.js features/ -p $profile -m $loadmethod
+    { set +x; } 2>/dev/null
+  done
+done