new(userspace/libsinsp): support lxc 4.0 cgroup layout. #6004

Job	Run time
build-libs-emscripten 🧐	4m 20s
build-libs-linux-amd64 😁 (system_deps)	6m 4s
build-libs-linux-amd64 😁 (bundled_deps)	18m 14s
build-libs-linux-amd64-static 🎃	24m 3s
build-libs-others-amd64 😨 (windows-latest, MultiThreaded)	5m 53s
build-libs-linux-amd64 😁 (system_deps_minimal)	4m 33s
build-shared-libs-linux-amd64 🧐	4m 42s
build-libs-others-amd64 😨 (windows-latest, MultiThreadedDLL)	5m 50s
build-libs-linux-amd64 😁 (sanitizers)	14m 20s
build-libs-others-amd64 😨 (macos-latest)	3m 35s
build-shared-libs-macos-amd64 😨	1m 36s
build-libs-linux-arm64 😁 (system_deps)	6m 6s
build-libs-linux-arm64 😁 (bundled_deps)	18m 10s
run-e2e-tests-amd64 (system_deps)	8m 50s
test-libs-static (bundled_deps)	15m 42s
build-libs-linux-arm64 😁 (system_deps_minimal)	4m 33s
run-e2e-tests-amd64 (bundled_deps)	20m 55s
build-libs-linux-arm64 😁 (sanitizers)	16m 31s
run-e2e-tests-amd64 (asan)	21m 58s
	3h 25m 55s

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