support cgroup2

* only shim v2 runc v2 ("io.containerd.runc.v2") is supported
* only PID metrics is implemented. Others should be implemented in separate PRs.
* lots of code duplication in v1 metrics and v2 metrics. Dedupe should be separate PR.

Signed-off-by: Akihiro Suda <akihiro.suda.cz@hco.ntt.co.jp>

vendor/github.com/cilium/ebpf/ptr_32_le.go

@@ -0,0 +1,14 @@
+// +build 386 amd64p32 arm mipsle mips64p32le
+
+package ebpf
+
+import (
+	"unsafe"
+)
+
+// ptr wraps an unsafe.Pointer to be 64bit to
+// conform to the syscall specification.
+type syscallPtr struct {
+	ptr unsafe.Pointer
+	pad uint32
+}